CHAPTER II

Darwin and Wallace

We have seen in the last chapter that whenever men have actively thought they have attempted to explain the origin of plants and animals as well as of themselves. No one who wrote previous to the time of Charles Darwin had expressed any idea concerning this matter with force enough to convince any large portion of the thinking world. If Lamarck had fallen on better times, if the great Cuvier had not laughed him to scorn, if Goethe had found him out and made him known to the world, evolution might have come into its own sooner. None of these conditions arose, and it remained for Charles Darwin to give to the world in clear and cogent form the thought of evolution. He gathered so much material before he expressed his opinions, and looked at the matter from so many sides that, when he published his results, he had foreseen most of the objections which were subsequently to arise in opposition to his announcement. Charles Darwin is recognized to-day as the father of the evolutionary movement.It has been sometimes said in recent years that Darwinism is dead, and there is a sense in which this is true. Unmodified and unassisted natural selection is not to-day considered by most scientists a sufficient agent for producing evolution. But everyone connected with the subject acknowledges Darwin as the master, and says that it was his work which converted the world to a belief in evolution. We can have no better preparation for an intelligent understanding of this subject than to consider carefully the life of this remarkable man and the circumstances under which he came to his epoch-making conclusions.

Evolution has taught us to attempt as far as may be to account for man on the basis of his heredity or of his environment. It is interesting to note that both of these factors in Darwin's case were entirely favorable. In the latter part of the eighteenth century Erasmus Darwin had given to the world an astonishing poem in which he anticipated not a little of the thought which his more famous grandson was to make so widely known. Josiah Wedgwood had learned to make for England her most famous pottery, no quality of which was more widely recognized than the sterling patience with which it was made. Erasmus Darwin, with his scientific proclivities, and Josiah Wedgwood, with his sturdy common sense and patient workmanship, united to give Charles Darwin his inherited tastes, for he was a grandson of both. Born in 1809, on the banks of the Severn in England, Charles Darwin was the delicate son of a practicing physician of modest but sufficient means. Owing to his lack of early vigor, Darwin spent much time in the open air, and in his excursions about his home was chiefly interested in collecting beetles. This taste, which lasted through all his young manhood, is the one early indication of the traits that were later to develop. At first in the day-school and later in the preparatory school Charles Darwin was anything but a satisfactory student. Even a kindly desire later to make the most of him makes it impossible to find traces of any especial fondness for earnest study. He himself believed his education to have been nearly useless, although he doubtless under-estimated its value. At the age of sixteen he went to Edinburgh at his father's desire, to study medicine. The sight of the dissecting-room nauseated him completely, and he refused to continue working in it. Later an operation which he witnessed in a clinic at the hospital sickened him so thoroughly that he declined to attend further operations. It became evident that the young man was not adapted to the life of a physician. The next move was to educate him for the church, and for this purpose, at the age of nineteen, he went to Cambridge. Here it soon appeared that he was no better adapted to the ministry than he was to the practice of medicine, and his university career went on in very desultory fashion. Most of his work was distinctly neglected, but two of the men he met there were to influence largely his future life. Henslow, the botanist, was unusually fond, for a professor in those days, of work in the field. Charles Darwin's tastes coincided with those of Henslow, with whom he formed an intimate friendship. He was always welcomed as a companion on the field trips. Though he studied little of botany in the classroom or laboratory, he was constantly with Henslow or with Sedgwick in the field. Sedgwick was the professor of geology, and of him Darwin was particularly fond, and under him did much the largest amount of his study. When he came up for graduation he ranked tenth of those who "did not go in for honors," a not very remarkable class standing. He was still required to put in two years of residence, and during this interval he spent most of his time with Sedgwick in the study of geology in the field. Returning to his home after a geological trip into Wales, Darwin found awaiting him a letter from Henslow, offering him an appointment that opened to his ardent mind the door to a career after his own heart.

The British nation, being the greatest commercial nation of the globe, has the greatest need for accurate charts of all the seas. Frequently she has sent out great charting expeditions to various parts of the world. One of these was to go out in Her Majesty's ship, Beagle, for a voyage around the world. Captain Fitzroy was in command, and he was especially commissioned to map the coast of South America from La Plata to Cape Horn and up the western side. In addition to this work, by carrying a set of accurate chronometers, he was to check up the longitude of the various ports to be visited in this circumnavigation of the globe. It was customary on such expeditions to carry a young man whose duty it was to study the natural history of the countries visited on the trip. The salary of such a naturalist was so small that an experienced man could scarcely afford to take the place. Therefore the appointment usually went to a man rather of promise than of achievement. Through Henslow's influence, Charles Darwin was offered this position in 1831. Darwin hastened to obtain his father's permission, but the elder Darwin at first declined to consider the matter. He felt that his son had not made such use of his time at the university as warranted the hope that much could be expected of such a journey. He believed it necessary that Charles should have some means of earning an adequate living before he could think of devoting his time to science. Charles found an efficient advocate in the person of his uncle, Josiah Wedgwood, Jr. Together they persuaded the father of the propriety of giving to Charles this opportunity to follow out his real tastes and ambitions. Accordingly, at the age of twenty-two, we find him embarked on a journey around the world. In the cabin of the Beagle he had abundant time, in his long sail across the Atlantic, to read the two volumes of Lyell's "Elements of Geology," which Henslow had handed him, with the suggestion that he read it, but on no account believe it. Filled with the love of geology as Darwin was, this epoch-making book was exactly the stimulus needed. Lyell had just begun to persuade the world that to understand the past we must study the present. In the forces now at work he saw cause enough to account for all the history of the past of the earth.

There is little doubt that this book was one of the most potent factors in determining the bent of Darwin's mind. His entire educational experience had failed to appeal to him. It is fortunate, we now know, that this was the case. If the university course of the time had really seized him it would have made but one more student like hundreds it was turning out each year. For most of us this is the happy event. Now and then comes the rare spirit to whom all of this fails to appeal because he is ready for something better. Such was the spirit of Charles Darwin. He started on his journey with a mind singularly free from prepossessions. In the long hours of this sailing voyage across the Atlantic Ocean Darwin had time to read and ponder Lyell's weighty words. By the time he reached the Brazilian shore he was filled with Lyell's conception that the present is the child of the past, developing out of it in orderly sequence. Lyell expressly denied that this is true of the animal and plant world. He applied it only to the face of the earth, with its mountains of uplift and its valleys of erosion. But the underlying principle of an orderly development under the action of natural causes was there. In Darwin's mind this at once found acceptance, and was destined to a fruition its author had expressly disclaimed.

The narrative of this voyage, as subsequently written, describes the islands visited by the Beagle in crossing the Atlantic Ocean. The contrast between the simple and general interest in these islands and the care with which Darwin described the Galapagos and the Keeling Atoll visited later in the voyage are speaking evidence of the rapid development going on in the mind of the young naturalist.

Reaching the shore of South America, Darwin first turns to its geology. But before long the animal life attracts his attention. In the Brazilian forest Darwin had his first experience of the wealth of animal and plant life in the tropics, and, like all naturalists, he was very enthusiastic over it. Among the animals that particularly attracted his attention was the sloth, a peculiar creature climbing slowly about the trees, small of size and sluggish of habit. Another animal that interested him greatly was the little armadillo with its interesting habit of curling up in its plated skin.

Captain Fitzroy soon finished what work he was required to do in this neighborhood, and Darwin was called back to the Beagle to continue his voyage. When they arrived at the mouth of La Plata their most serious work began. Here there was much tedious charting for Fitzroy, and Darwin could now leave the vessel for a lengthy trip on shore. This was doubly welcome. Seasickness was nearly constant with Darwin while on this entire voyage and every opportunity to work on land was eagerly seized. This region, too, was rich in objects of interest and in strange people. While exploring the pampas, beyond Buenos Ayres, Darwin came across the skeletons of the great mammals some of which Cuvier had previously described. He studied these bones with much care, and recognized at once in the megatherium a great similarity in structure to the sloth he had seen in Brazil. The enormous skeletons of the glyptodons struck him also as strangely similar to that of the armadillo. One evening, seated alone in the broad expanse of the pampas, the idea suddenly swept over him, stimulated, of course, by his study of Lyell: "Can it be that the little armadillo and the sloth of to-day are the degenerate descendants of the enormous megatherium and glyptodon of the past?" But his mind was not yet ready to accept so bold an idea and he swept it aside.

The people of this wild neighborhood interested Darwin very greatly, and he describes them with care. In this connection a charming trait of Darwin's character comes beautifully in evidence. The absolute purity of his mind, his utter freedom from grossness, shows clearly in his account of the first really semi-civilized people he had ever seen.

A little later, while exploring Patagonia, Darwin noticed the terrace-like formation of that desolate country. A flat near the sea was succeeded by a rapid rise, then came another flat. Three of these terraces in succession stretch back toward the Andes. At the base of the high terraces Darwin found marine shells, largely similar to those of the ocean beach so many miles to the east. His study of Lyell led him to suspect at once that this portion of South America had been raised in successive stages out of the bed of the Pacific. When they passed around Cape Horn and up the western coast he hunted for similar beach marks on the sheer western face of the Andes, and found them without difficulty, confirming his idea of the recent rise of this end of the Andean chain.

The Beagle continued its voyage up the western coast of South America until it reached Peru. Once more the abundance of tropical life is under Darwin's eyes, but now it is the life of an entirely different section. The dry climate of Peru furnished him with an environment distinctly unlike that of the moist Brazilian forest. He collects now with avidity, gathering especially insects and birds. Then the ship turned its prow westward across the Pacific, only to stop five hundred miles out at the Galapagos Islands. This little group he studied intensely, collecting large numbers of insects and birds. He had not worked over his collection long before he realized that each island in the group had peculiarities which marked its animals from those of any other island. Whenever two islands were close together in the group the differences in their fauna were found to be comparatively slight. If, however, he examined the animals from two islands lying at opposite ends of the group, the differences were always considerably greater. There was, however, a strong general resemblance among them all and a distant though not so strong resemblance to the corresponding animals of the Peruvian coast. On leaving the Galapagos group, Charles Darwin writes in his diary the suggestive observation that this little group of rocky islands seems to be one of the greatest centers of creative activity. It was this interesting resemblance of the animals of these islands to each other and to those of the Peruvian coast that finally persuaded Darwin that they were all related and were all descended from those of Peru. For the rest of his life, with an intensity which increased with each year, Darwin persisted in a patient search for the possible agencies by which such change could have been brought about. The problem, however, was temporarily eclipsed by a pressing geological question aroused by his visit to the Keeling Atoll. Here his investigation of coral reef formation absolutely captivated him. In the case of most coral islands in the Pacific Ocean the reef exists as a circle of coral enclosing a lagoon of water. In the center of this lagoon stands commonly a rocky island. It is plain that this is the foundation on which the coral built. But, in the case of the Atoll, the coral ring was present and so was the internal lagoon, but there was no rocky island. The key to the solution came with an interesting discovery. Darwin began to put down a grappling iron on the outer side of the reef and to drag up coral. The farther away from the reef he went the deeper was the water from whose bottom he pulled the coral. What at first puzzled him was the fact that so long as he dragged up his coral from depths of a hundred feet or less the coral was alive. Whenever he went to depths of much more than a hundred feet, his coral was always dead, though he was evidently pulling it from situations in which it had grown. Then Darwin remembered the rising Andes, lifting themselves out of the bed of the Pacific. Here was the correlated movement. The bottom of the ocean here was sinking. As it sank it dragged down the corals with it. But the descent was so slow that new corals could build on top of the others fast enough to keep the reef up to the surface of the water. At the rate of growth of coral, this would seem to mean that the bottom could be sinking at a rate of only a few feet a century. But while the reef could keep up to the surface, the rocky island must slowly sink. Darwin inferred that there must be a rocky summit within the lagoon, below the surface of the water. A little sounding soon discovered this island, and the verification of Darwin's theory of coral reef formation was at hand. The description of this Atoll and of his theory of its formation won for Darwin the esteem of geologists when he later presented it in book form.

The voyage was continued around the Cape of Good Hope. Pursuing the usual course of sailing vessels, the Beagle touched once more at Brazil, returning home to England in 1836, after an absence of five years. Charles Darwin himself believed this trip to have been both his education and his opportunity. He had started on it a rather careless and indifferent student. He returned from it the most painstaking and patient naturalist the world has ever known. His father, who had hardly consented to his going because he believed him not stable enough to be intrusted to his own devices for so long a period, was profoundly moved at the sight of him on his return. Believing in phrenology, as did many of the physicians of his time, his father turned to his mother and said, "Look at the shape of his head; it is quite altered"; which, translated into the language of to-day, would read, "How wonderfully the young man has developed."

A part of Charles Darwin's duty to the British Government was to write a narrative of the voyage, and this account of his trip upon the Beagle is one of the great classics of travel in the English language. It won the confidence and respect of a wide circle of readers. In his next book he published his observations made at the Keeling Atoll and announced his theory of the formation of coral islands. This was a distinctly scientific investigation, and it won such immediate favor among geologists as to increase materially the young man's reputation. No one man is ever widely enough acquainted with the animal world to classify all the specimens gathered on such an expedition. In accordance with custom, Darwin began distributing his collections among specialists. Each of these was to identify and describe, to name, if necessary, the kind of material he knew best. Among others, Darwin had a considerable collection of barnacles gathered from boats and wharves in all parts of the world. As he could find no one sufficiently acquainted with these creatures to classify them he decided reluctantly to work them up himself. For about eight years much of his spare time was given to this painfully exacting work. He expresses himself as fearing it was a waste of time. Few systematic workers will agree with him. He did his work so well that it has been unnecessary for anyone to do it again. In addition it gained him the esteem of a new circle of scientists and that a decidedly exclusive circle.

The publication of these books did much for Darwin. His narrative of the voyage gained the good will of cultured England in general. The book on coral reefs won the geologists. His "Manual of the Cirrhipedia" (as the barnacle book was called) secured the attention of systematic zoÖlogists. The time was not far distant when he would need every aid possible toward gaining and keeping the regard of men; for he was to promulgate a theory that would arouse the bitterest opposition and the keenest scorn.

All the while Darwin was working on these books his mind was quietly busying itself with what he called the species question. The more he studied the material collected on his long tour, the more confident he became that the animals of the present are the altered descendants of the animals of the past. He tried patiently to work out every conceivable hypothesis to see whether he could account for the alteration. He felt quite sure animals changed, but how they changed, and why, he could not for a long time conceive. He knew that gardeners were constantly producing new varieties of plants, and that animals of various breeds were clearly the descendants of other and familiar varieties. Accordingly he began to study the methods of animal and plant breeders, to visit their farms, to open correspondence with them and read all their trade journals, to undertake experiments in the breeding of plants. The longer he worked the more confident he became of the reality of the change; but for a long time no glimmer of the cause by which it could be brought about came to his mind. In 1838 he came across a book by Malthus called "An Essay on Population," in which the author shows that, whereas man increases by a geometric ratio, he cannot hope to increase his food supply in more than an arithmetic ratio. That is, while the food might increase like the series 2–4–6–8–10, the population would increase like the series 2–4–8–16–32. On this basis it is only a question of time when the earth will be too full of people for it to be possible for the food to sustain them. Malthus added many observations and suggestions, but this is as much of the book as interests us in this connection. Here was the idea that suggested to Darwin his agency for producing the change of the animals of the past into those of the present.

The number of animals of any particular species remains practically the same. There may be a few more one year, and a few less another, but on the average, year by year, the number of toads, the number of blacksnakes, the number of field mice, remains sensibly the same. Sometimes the rise of man brings an end to the wild population, and so in the past animals have dropped out of the race. Yet in the long run and for a considerable time the number of any species is constant. But each animal produces offspring in quantities sufficient to far more than replace himself as he dies out. In other words, animals increase not by addition but by multiplication. Too many are born for all of them to live. What becomes of the great mass of them? The answer is they die; most of them die young. Only a few fortunate individuals, favored by being a little stronger, a little more cunning, a little more attractively colored than their mates, survive to carry on the race.

The skillful gardener, looking over his flowers, finds a plant of more than ordinary beauty and thrift of growth. When it comes to maturity he keeps its seeds separate from those of the rest and next year plants them by themselves. As they come up he weeds out all unthrifty plants, only allowing the strongest to come to maturity. As they break into bloom he plucks away all whose flowers do not come up to the high standard he has set for himself. After a while he has but a few plants left, but these are the thriftiest and bear the most beautiful flowers. Again he allows these to mature and selects the seed of the very finest. Next year the process is repeated. After a few generations, usually three if the man is skillful enough, he has a definite strain of flowers that will thereafter come true. This is the process of artificial selection as carried on by man.

Darwin saw that Nature is constantly carrying on a similar process. She produces seeds enough on almost any plant to clothe the world in a few years if all of them could fall into proper ground and thrive like their parents. A friend of mine found a mullein stalk that bore more than seven hundred seed pods and averaged more than nine hundred seeds to the pod, a total of more than six hundred and thirty thousand seeds. If each of these could find lodgment on a plot eighteen inches square, produce a similar number of seeds and plant them all, the result would be overwhelming. The fourth generation would cover land and sea, from pole to pole, one hundred layers deep. But there is no such danger. Year by year the mulleins hold their own and no more. Any particular field may have more or less, but in the long run the average for a district is about the same. Some of the seeds are poor and thin. These scarcely sprout. Others spring up into thin-skinned plants, and the first frost nips them. Still others lack the woolly coating in its finest abundance, and the browsing animals eat these. Others lack power to put out a wide-ranging root supply and the first drought kills these. Still others fail to send up a vigorous stem and the passing animal knocks them over and they die. Of the few that are still surviving, some produce such small and inconspicuous blossoms that the insects scarcely see them, and they go unfertilized. In the end only the aristocrats of the group are left, aristocrats in the best sense of the word. These are strong, thrifty, and beautiful, and are provided with every defense known to the mullein world. From these the mulleins of the next generation will spring. Again Nature will select the best of these, by a repetition of the same process. Thus year by year the stock is improved. Any new feature that is favorable helps its possessor to survive, and, if happily mated, will show itself after a while in the entire group. This, in brief, is the underlying idea of Natural Selection, as Darwin conceived it.

In 1842, at Lyell's suggestion, Darwin wrote a short sketch of his ideas which he, two years later, expanded into a somewhat larger account. The manuscript of these early views of the theory was completely lost and has only been recovered within the last few years. It was recently published under the editorship of Charles Darwin's son, Francis. It is astonishing to see how clearly the first short sketch states the underlying conception which all of Darwin's subsequent work amplifies. Hooker was constantly urging Darwin to write out his whole theory in the form of a book, and Darwin had begun to do so in 1856.

Meanwhile, down in the Moluccas, Alfred Russell Wallace had been lying sick of a fever contracted during his exploring expedition in that neighborhood. He had been studying the distribution of the animal life of the Malay Archipelago. Overcome by sickness, as he lay in bed, he began to think over a book which he had read not long before, "Malthus on Population." Wallace had been pondering on the question of the origin of the animals of the Malay Archipelago. He had not the faintest knowledge of what Darwin was doing, but was influenced, of course, like Darwin, by what he read in Malthus. Interesting to relate, he had come to exactly the same conclusions, writing his opinions in the form of an essay. By the strangest sort of coincidence, he sent this essay to Charles Darwin, asking him to read it, and, if he thought it was not altogether too foolish, to send it to Lyell for publication by the LinnÆan Society. Darwin read with utter astonishment this essay containing views so absolutely like those that had come to him from his own long series of observations and reflections. With uncommon magnanimity his first impulse was to withhold his own publication entirely, but to this Lyell and Hooker would not for a moment consent. They were determined that Darwin should give them his long series of notebooks as evidence of the independence of his work and that he present to the LinnÆan Society, simultaneously with Wallace's paper, one of his own upon the same subject. In this manly form both essays were read at the next meeting of the society. The joint papers provoked instant discussion and prompt opposition. The world at large scarcely admitted a possible doubt of the fixity of species. Men generally believed the idea to be absolutely irreconcilable with their religious faith. Any question of the fact that the species of to-day exist practically as they had been handed down to the earth in the beginning by the Creator himself seemed to most men a direct blow at religion. At this time a very large number of natural scientists were clergymen, hence the opposition had abundant and influential support. The storm grew fiercer and more widespread. The publication in 1859 of Darwin's great book on "The Origin of Species by Means of Natural Selection or the Preservation of Favored Races in the Struggle for Life" added fuel to the flame.

In 1860 the British Association met in Oxford, and Bishop Wilberforce, the retiring president, in accordance with the custom of the society, gave a summary of the advance of science, especially during the preceding year. Everyone knew perfectly that the bishop would deal with the species question, and that he would handle it severely. Darwin was prevented by his usual ill health from being present at this meeting, but Huxley was there to see that their side of the question received proper attention. The bishop made a lengthy address, in the major portion of which he brought forward entirely worthy objections to Darwin's theories. Toward its close his feelings overmastered him and he departed from his manuscript and unburdened his mind. The lack of stenographers in those days and the tenseness of the moment, which made everyone forget to take down what was said, make it impossible to tell exactly what happened. It seems that Bishop Wilberforce, appealing to the prejudices of his audience, said, in language that now seems ludicrous but then was terribly bitter: "However, any of us might be willing to consider ourselves descended from an ape upon his father's side, no one would so demean his mother's memory as to imagine that she could possibly have shared in this descent." Huxley, who had waited patiently for the close of the bishop's address, saw immediately the fatal mistake. Turning to his companion beside him, he said, "The Lord has delivered the Philistine into my hands," and, rising, he hurled back at the bishop the indignant reply, "I should far rather owe my origin to an ape than I would owe it to a man who would use great gifts to obscure the truth." The bishop had made the mistake, and the struggle was on. Year by year it raged. One by one the scientists, first of England, and then of Germany, took their stand by Darwin. Huxley in England and Haeckel in Germany were the foremost advocates of the Darwinian idea. Long and fiercely the battle raged; slowly and gradually men began to see that, instead of undermining religion, the idea of evolution uplifted creation and made it not a strange happening in the distant past, but a divine activity through all time. But the battle had by no means subsided when one day came the sad news that Darwin's heart, so long feeble, so serious a hindrance to his work, had beaten its last on April 19, 1882.

His own people wished to bury Darwin quietly at his home in Down, but Darwin now belonged to the nation. A petition signed by many public men was sent to the Dean of Westminster, asking that his body might be granted burial in the Abbey. Probably no greater honor can come to man to-day, and fortunately Dean Bradbury was broad-minded enough to acquiesce. So it came to pass that the church that had so long believed him her enemy, that had first so bitterly fought him, came at length to see that he added a new dignity and worth to her faith, and took him to her bosom. Darwin's body lies buried in the Abbey.

In all the glorious company of immortal dead whose earthly frames are gathered in England's great mausoleum, there is no other one who has done so much to modify the mind of thinking man.

CHAPTER III

The Underlying Idea

We have seen in the preceding chapters how the idea of evolution worked its way through the minds of men. Man after man got a glimpse of the idea, even among the ancient philosophers. But no one could speak convincingly on the subject before modern times, when a wider acquaintance with the animal world gave a body of facts on which it was safe to base conclusions. Even then the idea eluded men, until there came a worker trained by a long voyage around the world in which he had nothing to do except to study nature. He finally gathered in his mind material sufficient to convince himself not only of the truth of evolution but of the process by which this evolution was brought about. Every scientific principle is simple in its basal idea. In actual life the action of the principle may be so bound up with others as to need a skillful mind for its detection. But under all the complexities and modifications, like a silver thread woven into a cloth, runs the basal idea. Until a master has detected it the presence of it may be unsuspected. But once discovered and expounded, thereafter anyone may follow out its workings. So it is with the Darwinian idea of selection. It waited long for a discoverer, but, once found, we cannot but wonder why men did not see it earlier, it is so simple.

Mr. Darwin's mind, while slow and cautious, had a wonderful perseverance. When he had finished his work he had not only given a clear account of the process of evolution, but he had foreseen almost all the valid objections that were afterward to be brought against his theory. Some of them he had explained quite fully; of others he indicated a possible explanation; of still other questions he confessed that as yet they were not plain. But the whole theory is so simple in its fundamental ideas that it has completely revolutionized the whole aspect of modern biology and, indeed, of modern thinking in many lines.

There are four underlying conceptions, each simple in itself, which must be clearly perceived before one can understand Mr. Darwin's theory of "Natural Selection." The first of these is known under the name of Heredity. It is a matter of common observation that every animal or plant produces offspring after its own kind. Under no conditions would we expect a duck to lay an egg from which could hatch anything but a duck. No Plymouth Rock chicken mated with another of her own kind will ever lay an egg that will produce a Rhode Island Red. We may believe that the dog has descended from some form of wolf, but it is not meant that at any particular time in the past any wolf mated with a wolf ever produced pups that were anything but wolves.

Why this should be so is one of the most profound problems of biology. Nothing but the fact that the process has gone on under our eyes for so long a time could blind us to its marvelous character. To open the egg of a chicken and examine it by the most refined methods known to science is to find in it absolutely nothing that could be by the widest stretch of the imagination considered anything like a chicken. The biologist who has examined such eggs before and knows them in all stages of the process may recognize in an egg which had been incubated for a short time something which his previous experience tells him will become a chicken. But it has not the faintest resemblance to a chicken until later in its development. In early spring one may gather pond snails from any country stream and place them in an aquarium. The change from the cold water on the outside to the warmer water of the aquarium and the temperate climate of the room hastens the process which in the stream would not take place until later. In a short time one may find fastened to the glass side of the aquarium the little mass of transparent jelly which surrounds and protects the delicate eggs of these creatures. Fastened as they are it is easy to direct a magnifying glass so as to observe the change which goes on within these transparent eggs. It is even possible to apply a microscope in such a way as to watch the transformation under the low power of the glass. At first the eggs are as clear as water, having at the center a slightly yellowish spot. This central mass divides and subdivides until the separated sections grow so small and numerous as to lose individuality. Then the mass begins to press out here and dent in there. After a little while a double line of fine, hairlike projections runs around the creature. These hairs wave in such fashion as to make the embryo snail revolve slowly in its egg. A little later and swellings become more pronounced over the surface. One side flattens; the rotary motion stops; eyes appear at the front of the animal; a hump on the back begins to be covered with a shell, and the little creatures, pushing from the jelly, start their life journey on the side of the aquarium. Why did it happen? How did it happen? Here we have seen creation at work. Here surely the hand of the Creator is working in the only sense in which the Creator may be properly said to have a hand. How the history of the substance out of which the egg was produced provides for the future development of that egg no man has yet clearly said. This is not to say that we shall never know, still less is it to say that this can never be known. Ralph Waldo Emerson has said that there is no question propounded by the order of nature which the order of nature will not at some time solve. If he is right, and I believe he is, we shall at some time know how it is that this egg produces this snail. But, as I said before, nothing but the frequency with which the process goes on under our eyes could possibly blind us to the marvel of it.

The regularity with which each animal reproduces its kind is no more surprising than the faithfulness of that reproduction. Some of our birds have wonderful markings on their plumage. It is astonishing to see with what fidelity the feather of a bird may reproduce the corresponding feather of its parent. It will occur to everyone how, in the human family to which he belongs, there is some little peculiarity which, while not appearing in every member of the family, when it does appear is remarkably uniform. It may be only the droop of an eyelid, it may be a tendency to lift one side of the lip more than the other, it may be the peculiar shape of a certain tooth in the set, and yet when it appears it comes with astonishing similarity in all who possess it. So much for the principle of Heredity.The second great underlying idea is known by the name of Variation. We have just been dwelling on the regularity with which parents produce offspring like themselves. We must now draw attention to the fact that, while it is true animals must absolutely belong to the same genus or species, even to the same variety, none the less no animal is exactly like his parents. Furthermore, in a group of animals produced at the same time from the same parent each one will have at least some small point in which he differs from every other one in the group. Two animals may look alike at first to the undiscerning eye, but a keen analysis of the measurements of the various parts of their bodies will show distinct differences. This is quite as true among lower animals. A toad may lay a double string of four hundred eggs which may be fertilized by the same male at the same time. These eggs may develop into tadpoles in the same pool not over a foot square. Within a few weeks these little toads may have gained their legs, lost their tails, and all may have left the water and taken to the ground upon the same day. Already the careful observer will notice differences among them. Some are larger than others, having grown more rapidly even though their surroundings were exactly the same; others are more skillful in their peculiar method of throwing the tongue at an insect they wish to catch. Still others will be differently colored. They might be arranged to show a considerable gradation between the lightest and the darkest of the group, though there may not be anywhere in the row a considerable gap. It is variation in animals of the same parentage and same surroundings which in the mind of Mr. Darwin made evolution possible. He always favored the idea that it was the continuous accumulation of these small variations that finally produced the profound changes which mark the new species. He admitted the possibility of the occasional appearance of those more distinct leaps in variation on which the present school of mutationists so strongly insists; but he believed them to be less influential, in the general trend of evolution, than the slower but much more frequent variations.

One of the most complicated and perplexing problems in the biology of to-day is the question of the origin of these variations. It is quite as hard to understand as is the method by which animals produce their own kind. No problem is being more earnestly studied. Suppositions we have in considerable number, and two of these at least may reasonably be mentioned. We will consider first the less certain theory. There is nothing in the egg that in the remotest degree resembles its parent. The old idea that every acorn had in it a miniature oak which only needed to unfold itself, or that the hen's egg had within it a miniature chick which only needed the warming process in order to make it evident, could not possibly survive the invention of the microscope. We may not, and we certainly do not, know everything that is in one of these eggs, but we do know most certainly that what is there has no resemblance to what it will be in time. The biologist finds in the nucleus or central core of every growing and reproducing cell certain minute bodies which Weissmann believes do much to determine the growth of the rest of the cell. He believes also that there are many more such "determinants" than are necessary for the reproduction of the cell. Each of these determinants may be fitted to produce slightly different results, but what decides which of them shall have its own way is quite uncertain. It may be that one determinant happens to be more favorably placed than others in the cell and that it has consequently secured more of the nourishment that comes to the cell in the blood of its parent. If this is true it would certainly be favored in the competition. We are becoming quite certain that whatever variations arise really start in the egg. The simplest conception as to the cause of variation would seem to be varied experience. One man trains his brain, another his hand; and in each case the organ so trained develops. But science is strongly of the mind that such influence does not reach the next generation.

A musician may have taught his fingers to be nimble; may have given them speed of motion and precision in their action. No child of his born after he acquired this wonderful facility of execution is any more likely to be a skilled musician than a child born before he had ever practiced enough to be anything more than a crude performer. Science is nearly certain that his children are just as likely to be talented along musical lines if he himself never had become a musician, simply because he had it in him to be a musician. In other words, they may inherit the talent which he developed, but they inherited it not because he developed it, but because it was in him to be developed. This is in accordance with the famous principle that there is no inheritance of acquired characters. We shall touch this question a little more fully in a later chapter, in speaking of the development of the evolution theory since Darwin's time.

If we are right in this matter, and we certainly are nearly right, variation must take place for the most part in the germ. These variations may not show until the animal has grown up, but they must have taken place among the determinants in the germ cell or they would not reappear in subsequent generations.There is another process by which new variations may arise and which is more easily understood. It is the method of double parentage. The Barred Plymouth Rock chicken had its origin in such a double ancestry. The one parent was a Black Java whose color has disappeared entirely in the cross, but whose single comb with its few large points comes out clearly in the newly produced fowl. The other parent was a Barred Dominique. It is to this parent that the Plymouth Rock owes the interesting cross markings on its feathers. The comb on the head of the Barred Dominique is of the type known as the rose-comb, having many rows of slight projections. This has completely disappeared from the Plymouth Rock fowls. I am told that the skilled chicken fancier can tell, concerning many points in this fowl, to which of the crossed ancestors each quality is due. To a certain extent it is undoubtedly true that here we have the secret of the origin of many of those interesting people whom we are pleased to call geniuses. They may not possess any qualities not clearly discernible in various of their near ancestors, but in them we find what we, for the lack of a better understanding, call chance combination in one individual of the finer qualities of many ancestors, and this individual is so placed in life as to have these qualities developed and strengthened.Charles Darwin, humanly speaking, may be accounted for as the happy combination of a double heredity and a favorable environment. He inherited the scientific inclinations of his grandfather, Erasmus Darwin, and the patient, sturdy honesty of his other grandfather, Josiah Wedgwood. These developed under the stimulus of the long five-year voyage, face to face with the world of nature. This happy complex produced the master biologist. To believe that he came about purely by chance requires a great stretch of the imagination. "There's a divinity that shapes our ends."

We have endeavored to make clear two of the basal ideas underlying evolution. One of these is responsible for the continued production of animals or plants of the same kind, preventing the world from becoming a wild kaleidoscopic and fantastic dream. Heredity is the conservative force of nature. The other idea underlies the development of new departures which keep the world from being a dull, dead, unending repetition of the same monotonous material. Variation is the progressive tendency in nature.

The third basal idea is that of Multiplication. Animals and plants multiply; they do not simply increase, they increase in a geometrical ratio. Anyone who has worked out one of these geometrical ratios knows how wondrously they mount up. There is an old familiar story of the blacksmith who asked the price at which the stranger would sell the horse he was shoeing. The owner of the horse replied that, if the blacksmith would give him one penny for the first nail he drove into the shoe, two for the second, four for the third, and so on, he might have the horse. No hundred horses in the world taken together have ever brought such a price as the blacksmith would have had to pay for the animal on which he was working. This is no circumstance to the awful story of what would happen to the earth if any animal could multiply unrestricted. The usual number of eggs laid by a mother robin for a single brood is four, and she may produce two broods in one season. This would mean that the original pair had produced eight offspring, four times their own number. If we can imagine these mating the next year and producing their kind in the same proportion; and, if we further suppose that each robin needs a space one hundred feet square from which to gather his food, we realize the astonishing fact that in fifteen years every patch one hundred feet square in Pennsylvania and New York would each have its resident robin, while the following season would find a robin on every similar patch from Maine to the Carolinas. Of course this could never happen, this is simply what would happen if all the robins could grow to maturity and reproduce at the normal ratio. But the robin is a comparatively slow producer.

Our turtles are more prolific. Twenty eggs would probably not be an unusual number. If we could imagine a turtle to live in the sea and to produce at this rate; and, if each turtle should need as much room each way as the robin, and a depth of water equal to its width, before the robins had spread over New York and Pennsylvania the turtles would have filled all the seas of the globe. Frogs are even more remarkable in this respect. Two hundred eggs is not an uncommon number. If each frog required a space twenty-five feet square on which to subsist, the entire earth would be more than covered with them within six years. It is ludicrous to think of such numbers, especially when we realize the hundreds of thousands of kinds of animals there are in the world, each of which is also multiplying, and it becomes evident at once that only an infinitely small proportion of all these creatures can possibly survive. This, then, is multiplication.

Here comes into play the fourth basal idea in Mr. Darwin's explanation. This is the part of Selection. When man produces new varieties of animals he does it by picking out from his flocks or his herds such as conform most nearly to his idea of what is desirable. These he mates, and from their progeny he selects the ones that suit him best. Generation by generation he gets his domesticated animals to conform more nearly to the standard of his desires. Natural selection works in exactly similar fashion. Of all the eggs that are produced by the animals at large in nature an overwhelming proportion never develop at all. They dry up, are eaten by their enemies, find no suitable place or time for development and decay, or are overtaken by some other calamity. Of the animals which emerge from the remainder an overwhelming majority come to an untimely end within the first few days of life. Each has countless enemies which prey upon him, and these have scarcely devoured him before they themselves become the prey of some stronger creature. Until Mr. Darwin gave us his elemental idea it was taken for granted that it was a matter of pure accident which survived and which yielded in the struggle and cares of life. It was Darwin who showed us that in this tremendous struggle against those of his own kind in the search for the same food, against the elements, in securing a mate, any animals possessing a superiority, however slight, must have some little advantage in the battle. Certainly, where so many must utterly fail, only those could possibly succeed who were well fitted to the circumstances in which they must live. We used to think animals were destroyed by the "accidents" of life and no one could foretell accidents. Mr. Darwin made clear that it was not a question of chance. That which might happen to any individual animal might be what we, not knowing the process, called accident, and yet there could be no possible doubt that those who succeeded were better fitted to battle with life than those who failed, and that their success was due primarily to their being thus advantaged. Consequently, if generation by generation the so-called accidents of life are constantly eliminating the unfit in overwhelming proportions, not only must the positively unfit disappear, but even the less fit. The more keen the struggle, the fewer could survive and the fitter they must be to survive at all. This is Selection. These, then, are Darwin's four great factors of evolution: Heredity, Variation, Multiplication, Selection.

From these it results that the animals and plants naturally become better adapted to the situation in which they are placed. When, as is constantly happening through the history of the earth, a change occurs in the physical geography of any region, when a plain is lifted to be a plateau, or a mountain chain is submerged until it becomes a row of small islands, this alteration will produce uncommon hardships among animals, even though they were well fitted to the old conditions. Any animal or any species of animals which meets such a calamity has before it only three possible outcomes of the struggle. First it may be plastic enough and it may vary enough in the right direction to adjust itself to the changed conditions. In this case it and a favored few like it will occupy the altered territory. The second possibility is that it may migrate while the actual change is going on, thus remaining in the sort of situation suited to it and its kind. The third possibility is the one which overtakes a great majority of animals—they die. Even the entire line dies out, and the strata of the rocks are filled with the bones, shells, and teeth of such as have met this fate. They have become extinct.

Thus far in this chapter we have been considering the influences under which it is conceivable that animals should advance. There is no question whatever that there are too many animals born, nor is there any possible question that a very large proportion of them must certainly die. There is equally no doubt that every animal produces after its own kind, and that its offspring, while they resemble it closely, still vary a little from it and from each other. This fact is perfectly plain to the most superficial observer who thinks on the matter at all. It is not so plain, nor is it easily demonstrated, that all of these acting together do surely, even if slowly, alter the form and behavior of the animal world. It is difficult to prove that there is going on under our eyes a steady and real improvement in the adaptation of the animals and plants around us to the situation in which they are placed. As far back as man's memory runs they seem to have been about what they now are; as far even as man's historical record runs they seem to have suffered no great alteration. The Egyptian of the old tombs is much like the Egyptian of the same rank to-day. The African of the tombs has the African features of to-day. Under such circumstances it is hard to prove that there is a steady and undoubted advance. For the most part the balance of the animal world is fairly even, and any species does not ordinarily change rapidly enough or migrate widely enough to show us its new features. It is difficult to see the struggle which we are so sure is going on. The life of animals is so hidden in many of its details that their joys and sorrows, if such we may call them, scarcely fall under our observation. Now and then an opportunity comes to see the process of adaptation work itself out. The struggle for existence begins anew and is carried on with special vigor, with victory, temporary or permanent, to one of the participants in the struggle.

The opportunity to observe such a change is presented in the United States by the introduction of the so-called English sparrow. This little creature, received at first with such joy, soon became the object of an almost bitter hatred on the part of very many people. This is really due to the fact that this bird is one of nature's darlings and thoroughly succeeds where it has an even chance.

The number of birds of any particular species which a region will support seems to be fairly definite. If a species is especially protected until it becomes unusually abundant, the removal of the protection commonly brings it down promptly to its original numbers. On the other hand, an accident of severe character or a special persecution may much diminish the number of the species, and still it will, within a comparatively few years, return to its previous abundance.

The inhabitants of Florida who own orange groves will never forget the winter of '94–5. A bitter cold wave swept along the coast and killed such large numbers of orange trees as almost to cut Florida out of the orange market and to open the gate to California, who was eagerly offering her fruit. This same frost caught the migrating blue birds and killed them by the thousands. When spring came bird-lovers throughout the eastern United States found an astonishing scarcity of these favorites. It was feared that with numbers so small they could not possibly compete with their enemies and with whatever untoward circumstances should be their lot. But there is room in this environment for a definite number of bluebirds. When this number was suddenly reduced the chances to make a bluebird's living were so wondrously multiplied that young bluebirds had such an opportunity in life as their fellows had not had for many long years. Accordingly they thrived as never before, and, of their progeny, a larger proportion lived to the following year. It was only a few years before the number of bluebirds had risen. Now we probably have as many as we have had for a long time past. I cite this simply to show that a region can support a certain number of animals of any one particular kind, and that the animal is likely to multiply, if given a fair chance, until it has reached such proportions. Now to my story of the rapid development of a newcomer.

In the year 1850 a resident of Brooklyn came home from a trip to Europe. He was a lover of birds, and while in Europe had been particularly attracted, no one now knows quite why, to the common House Sparrow, as it should be called. It is no more abundant in England than in many parts of the continent of Europe. A name that has been used for a long time is very hard to cast aside, and we shall probably continue to mistakenly call him the English Sparrow to the end. Our Brooklyn traveler brought home with him from Europe eight of these interesting little birds and succeeded in inducing his colleagues in a scientific society to share his interest in them. Not wishing to commit the newcomers suddenly to the rigors of the American winter, these men built a large cage for the sparrows, meaning to set them free in the spring. For some reason or other when the winter was over the birds were all dead, and this first attempt to introduce the sparrow into America failed entirely. The little bird had won so many friends that his success was now sure. Finding a favorable opportunity, these Brooklyn men dispatched an order to a man in Europe, asking him to supply them with one hundred English sparrows. The consignment came in good shape and the birds were liberated on the edge of Brooklyn. This was the first of a number of introductions. A little later New York City sent for two hundred and twenty of these interesting creatures and turned them loose in her parks, while Rochester, with what was then considered great public spirit, purchased one hundred for herself. But the most progressive city in this respect was Philadelphia. She had long been troubled with the spanworm on her trees. This detestable larva had the unpleasant fashion of lowering itself by a long silken thread from the shade trees then so abundant in that beautiful city. The spanworms traveling around over the clothing of the passersby were so objectionable to everybody that it was with greatest delight that Philadelphia heard of the new birds which ate the pest. One wonders why some ornithologist did not look at the bird long enough to see that it had the sort of a bill characteristic of birds that eat seeds. It is true that most birds feed their young on insects, hence there is a time when any bird is apt to be insectivorous. But the structure of the sparrow's bill, like that of all finches, should have warned these bird-lovers that the sparrow was not to be depended upon to earn his living by catching worms. It is easy, however, to be wise after the event. Philadelphia believed she was engaging in a particularly advanced movement when she imported from England one thousand English sparrows, nearly as many as were liberated by all other cities together. These birds were turned loose among the shady streets and wide spreading parks of the City of Brotherly Love.

It is a serious matter lightly to disturb the balance of nature by the introduction of a new species. It is true that the sparrow did eat some spanworms and for a while enthusiastic bird-lovers hoped that here was the solution of the difficulty. Philadelphians will also remember that, with the spanworm removed from competition, the tussock moth, whose caterpillar carries on his back a series of yellow, red, and black paint brushes, at once become the permanent parasite of the long-suffering shade trees. This caterpillar is covered with bristling hairs, very closely set. Almost any bird objects to hair in his victuals; and this particular larva has hair more than ordinarily objectionable, for it irritates wherever it pricks the sensitive skin. This coating seems to protect the caterpillar from the sparrow, with the result that Philadelphia's trees were soon nearly defoliated by this comparatively new pest, worse than the spanworm. With the paving of the city's highways and the consequent shutting off of the air from the roots, the trees have largely disappeared from the streets of Philadelphia. With them have gone a fair portion of the tussock worms, but the sparrow holds his own. Here is a new bird in the field, and the struggle for existence on the part of every other kind of bird is now more complicated and severe. The sparrow can live where the rest of the birds have no possible chance. He throve so well in this country that by 1875 he had spread over five hundred square miles in the neighborhood of our larger Eastern cities. Thus far almost everybody was pleased with the new introduction. Within the next five years he had spread over more than fifteen thousand square miles, and wise men were beginning to feel doubtful of the virtues of their aforetime friend. When by 1885 more than five hundred thousand square miles had been occupied by the enterprising little fellow, there remained no longer a doubt in the minds of most people that the sparrow was an unmitigated nuisance and great fears were entertained that he had multiplied to such an extent as to be a serious menace. Here, then, is a modern instance under our own eyes of a victory in the struggle. If the sparrow has multiplied rapidly, while all the other birds have either only held their own or even have diminished in numbers, it is quite evident he must be better fitted to the conditions than they are. What are his fit points? Why does he succeed while others fail? The thoughtful bird-lover will have little trouble in understanding at least some of his victory-winning characteristics. How did he come to be almost the only bird who can live in large numbers in our great cities, without losing his ability to get along in less crowded situations?

In the first place this interesting bird is a clannish fellow. He has lost the ordinary sparrow habit and has come to like to live in crowded groups. Seclusion is not at all to his taste, and if there are only a few sparrows in the neighborhood those few will most certainly be found living near each other. One of the early adaptations of the sparrow to his city surroundings was the ability to find for himself a considerable proportion of his food in the undigested seed that could be picked up from the droppings of the horses. This naturally led the surplus sparrows out through the many thoroughfares leading from any large city. Where horses went sparrows could follow. Accordingly along the great lines of travel this bird found the simple path by which he could enter new territory. Meanwhile box-cars came into our large cities with freight. Sometimes they had carried grain, sometimes cattle. In either case it was not unlikely that a certain amount of grain should be found scattered over the floor of such cars. The sparrow visited these cars for the grain, and it must have been no infrequent accident that a door should be shut upon a group of sparrows, especially in inclement weather, when they were apt to be huddled in a dark corner of the car. These prisoners would be carried to the destination of the car and there liberated, thus producing a new center of what we are now inclined to call infestation. By such means the English sparrow has spread over much the larger portion of the American continent. Few birds are bold enough to visit a railroad car. Of the few who might be tempted, most are timid enough to fly on the first approach of man. Hence they fail to gain this chance of spreading. They must remain in the old crowded home. Meanwhile the sparrow, thus transported, finds a new home with fewer or no sparrows. The struggle is less keen. More of his kind can live. His boldness has been here a fit quality and has helped him in the race.

Man is only slowly coming to be a city-dwelling animal. Although it is a voluntary process with him, he still usually visits the country with much enjoyment. He has not as yet learned to adapt himself thoroughly to the city, for somehow city life kills him. Families that move into the city gradually have a smaller number of children in each generation until shortly the family is wiped out. The population of the city must constantly be replenished from the country. But the English sparrow is more adaptable than are the people. He has made himself at home in the heart of the biggest city. The Wall Street canyon is not deep enough, nor contracted enough, nor free enough of food to blot out the life of the English sparrow. At the heart of the deepest gully among the skyscrapers of our biggest cities we find this little bird hopping between the horses' feet, darting out from under the wheel of the push-cart, fluttering only a few yards to a place of safety, to return at once to his scanty meal upon the pavement as soon as opportunity offers. He is a typical city dweller and has learned to thrive there. Again in this matter he has distanced other birds to whom the city is more deadly than it is to people.

Another very important element in his fitness for the struggle of life lies in the fact that he is unafraid of man. He is wary of man; by which I mean he will quickly fly up from in front of man's feet. It is exceedingly difficult to catch a sparrow in one's hand. It is far easier to lure a pigeon within reach. But the sparrow, when escaping your hands, comes to rest but a slight distance away, only to elude you quite as successfully if you try again. If the sparrow is let severely alone he becomes more and more familiar with men, flies less promptly, and goes a shorter distance, but any attempt to trap him renders him shy more quickly than almost any other bird we have. He soon learns to avoid a trap in which his companions have come to grief. Those who would poison or trap sparrows must change constantly the base of their operations. This fearlessness of man is a valuable asset to the bird, for it is an important defense against other foes.

The most serious enemy the birds at large have, after man himself, is the bird of prey. Hawks and owls capture a large quantity of our smaller birds. Now the hawks and owls are for the most part shy of man. They have gotten a bad reputation, especially if they are of any size, because of their more or less pronounced proclivities for seizing our domestic poultry, and consequently many people will fire upon a hawk or an owl who would probably fire upon no other bird. By living close to man the sparrow is largely saved from the danger of capture by these carnivorous creatures, and this is the first and a very important element of the advantage to the sparrow of living near man. But there is the additional advantage that man scatters about him, in one way or another, a very considerable amount of waste food. I have suggested that the seeds in the droppings of the horse form a large proportion of the sparrow's food, and horses are to be found only with men. In the neighborhood of man's home, unless he has become sanitary to a degree which has only been attained in recent years, there is usually more or less garbage, kitchen offal of one sort or another. To this the sparrow has easy access and from it he makes many a meal. But this fearlessness of man gives him still another advantage which his competitors fear to use, it provides him with nesting sites.

Man has the faculty of putting up ornamental trimmings on his house, and there is no spot the sparrow chooses more willingly in which to build his nest than the ornamental quirks and cornices of man's architecture. A Corinthian column with comely leaves in its capital seems especially designed for the comfort of the sparrow, and his distinctly untidy nest is the familiar disfigurement of almost every ornate public building. These are the advantages which come to the sparrow from his willingness to associate with man, and there are comparatively few birds with whom he must share them. Few birds select the immediate neighborhood of man's home for their nests. They may live in the neighboring trees, they may haunt his orchard, but his house, for the most part, they decline to frequent.

Still another quality which makes for success in this buccaneer is the willingness with which he will vary his food as occasion requires. It is a not infrequent characteristic of the bird family that each species should have its own rather restricted diet. Birds are quite particular eaters, and many of them will come well nigh to starvation before they will use unaccustomed food. The sparrow, on the contrary, like man, eats almost anything he comes across that could reasonably be considered edible. He belongs to a group of birds which are structurally adapted to cracking the hard coats of seeds. This group of birds known as the finches is provided with the sort of bill familiar in the ordinary canary bird. It is short, heavy at the base, comes quickly to a point, and is firm and strong. With it the bird readily breaks through the hard outer coat of most seeds and feeds upon the rich cotyledons that are enclosed within. Nowhere in its entire structure does the plant crowd so much nourishment in so little space as it does in the seeds. It is not by chance that the great human food is grain. The sparrow belongs to the one bird group that makes a specialty of such seeds.

Most of the English sparrow's cousins in this finch group confine themselves rather rigidly to this diet. Here the variability of the sparrow again gives him the advantage. He may have the family fondness for seeds, but in their absence he can be content with almost anything edible. In the early springtime, when the seeds of last year are gone and those of the new year have not yet been produced, the sparrow is not averse to eating young buds from the trees. At this time he is not unlikely to eat our sprouting lettuce and peas. It is easy to be severe on him in this matter; but for a creature like man, who has the same tastes, who eats the enormous buds of the cabbage, the cauliflower, and the brussels sprouts, or the more tender buds which he calls heads of lettuce, it seems particularly inappropriate that he should throw stones at this little creature whose tastes are so similar to his own.

While seeds are more suitable for an elder bird they are altogether too indigestible to be the food of nestlings. So when the sparrow finds its nest full we know he must sally forth in search of nourishment more simple of digestion. Now for a few weeks he searches assiduously, catching insects and caterpillars of various kinds, and feeds them to his young. This taste passes as his children grow older, especially as shortly the seeds begin to ripen. Now is the time for the sparrow to fatten. Now he is eating the food for which he was really built. By the time the wheat is ripe there are sparrows enough about to form quite a flock, and when these settle down in a wheat, rye, or oats field and feed upon the grain, meanwhile shaking out upon the ground perhaps as much as they eat, the farmer begins to realize that the sparrow is not his friend.

When winter comes the struggle for existence among the birds is intensified, and comparatively few of them dare face it. Most of our birds betake themselves to less rigorous quarters, leaving to the sparrow a comparatively small number of competitors for the diminished supply of food. As long as the snow is off the ground the sparrows can find sufficient sustenance. They gather themselves into groups and sally out from the city into the open country. The immediate result is that great quantities of weed seeds are seized upon by the English sparrow, as, indeed, by every other finch which is with us in winter. Perhaps we have not given the little fellow credit for the good he does at this particular time, for the rest of the account truly does not help him in our esteem.

There is a further direct advantage in the sparrow's sociability. One robin may nest in the vines about your porch. If there were room for a dozen, scarcely more than one would be likely to use it, because he would drive away any other robin who attempted to share the neighborhood with him. To the sparrow company is always in order. While he may quarrel from morning until night with his fellow, it is a sociable quarrel and neither would willingly forgo it. This union is strength among birds, as with man. Every animal is safer from his enemies when he can have the constant presence of others of his own kind. The deer that stays in the herd is safer from the wolves. It is only when the latter succeed in cutting out some weaker or less sagacious animal that these carnivorous creatures succeed in tearing down their prey. I think the superiority of the sparrow over most of our common birds, when considered as a city dweller, is scarcely understood. Because he had won in the race with other birds is no necessary indication that he warred directly against them. Bird-men often attribute to him a quarrelsome disposition, as if he actually drove other birds away. It almost seems like animosity against the sparrow to speak of him as attacking blackbirds and crows. It is a cowardly crow who can be driven away by a sparrow, and if the two cannot live together it seems to me certainly to the discredit of the crow and not of the sparrow. I believe the truth to be that, while the sparrow is undoubtedly a quarrelsome fellow, his bickerings are his form of social converse with those of his own kind. A quarrel among themselves seems not to indicate animosity, but would appear to be the sparrow's idea of conviviality. It rarely leads to serious results. I have never seen a male sparrow trounce any other bird with half the vigor that I have occasionally seen the mother sparrow evince when she caught her male companion by the feathers of his head, hung him over the side of the limb, and vigorously and thoroughly shook him until he desisted from his annoying and possibly insulting attentions. The truth of the matter is that a colony of these little birds, with their continual social chatter, including their quarrels, makes such a continuous noise that the ordinary bird, which is generally of rather quiet disposition, is too much annoyed by the unending nuisance to find the neighborhood at all to his taste. Where a large number of sparrows have gathered together the conditions are such as would give a robin or a bluebird nervous prostration, and his only recourse is to depart to a neighborhood where there is more peace and quiet. But our English sparrow is not only better fitted for the struggle than the robins and bluebirds, the orioles and the wrens. He has one important advantage over even his own sparrow cousins. The males are handsome—much more so than the females or than their sparrow cousins in general.

In the song sparrow, field sparrow, chipping sparrow, and the fox sparrow the male and female are very nearly alike in color. It often becomes necessary for the bird-man to examine the internal organs of the bird he is stuffing before he can certainly decide its sex. But there is no difficulty whatever in telling the male from the female of the English sparrow. The male is far the more ornate bird. His back is striped with a richer brown; his head has two splendid dashes of chestnut over the eyes; his throat and breast are splashed with red and lustrous black; his bill is a clear fine black. Altogether the bird is strikingly colored for a sparrow, and this characteristic is the more remarkable when we see how quiet and somber is his more modest mate. This brilliancy of male plumage in the presence of the somber color of his mate would seem to indicate that the English sparrow is eye-minded rather than ear-minded. It is true among human beings that most of them are eye-minded. That is to say, they notice things with their eyes chiefly. Memories they have are memories of things seen; recollections of their friends bring up the appearance of their friends. Their language is full of metaphors which imply form and shape. But occasionally we come across an ear-minded person. He remembers voices quite as well as he remembers faces. To him music is an unending delight, and painting and sculpture fall into a distinctly secondary place. This is ear-mindedness. Now, most of the sparrows seem to be ear-minded, at least as far as their recognition of their mates are concerned. In this group beauty of song is developed many times oftener than is especial ornateness of plumage. The bird-lover who is himself keen of ear is never tired of listening, when in the field, for the two low notes with which the vesper sparrow introduces a song, the rest of which is not at all unlike the one of his song-sparrow cousin. The field sparrow begins more like the song sparrow, but ends with an often repeated note, which not a little resembles in general character the somewhat more monotonous song of the grasshopper sparrow or of the chippy. In comparison with these melodious birds the English sparrow makes no showing whatever. His voice is harsh and querulous, although very occasionally it is possible for the bird-lover to detect a note or two which would indicate that, if he were properly educated, his voice might amount to something. He wins his wife not by his pleasant voice, but by his attractive appearance and his winning ways. We have every right to infer from the character of its fellow birds of the sparrow family that once the female and male sparrow were colored about alike. But Madam English Sparrow was apparently eye-minded rather than ear-minded. Whatever pleasant voice a suitor might have seems to have been to her without attraction, and there was nothing to encourage him in developing it, nor was she likely to mate with him for it and transmit it to her male children. On the other hand, let a suitor appear in whom a more brilliant coloring proclaimed his superior vigor, and this seems to catch her eye at once. The less accomplished rival in the tournament of love seems to have been already forgotten. To their children these successful characteristics were naturally handed on and led to equal success on their part. If any of these children possessed this badge of honor in a more than ordinary degree, he was the more likely to win a mate and thus again the opportunity of passing on to his offspring his own distinct advantage. Generation by generation the males have become more beautiful and the females more discriminating. That the bird is either instinctively or actually conscious of this advantage would appear from the constant fluffing of his feathers and spreading of his highly colored wings with which he evinces his admiration for his ladylove. Even the most hardened dweller in the city can scarcely have failed to see the sparrow spread his wings, fluff his feathers, and sink close to the ground, twirling and gyrating about the object of his affection. It must give him a shock to see how often she proves temporarily or hypocritically indifferent to the demonstrative proceedings. Indeed they may terminate in a thorough trouncing of the male on the part of the lady of his affections. Now this preference for color over song must have evidently evolved in connection with the development of social habits in the English sparrows. His cousins of the fields, our native sparrows, are much less social, much less likely to be met with in flocks. To birds who scatter more, beautiful song is a great advantage. It can be heard at a long distance. But when birds flock together a much better advantage is that of beautiful clothing, added to alluring ways.

But we have not nearly exhausted the catalogue of the traits belonging to our little friend which give him the advantage over other birds in the struggle for life. His ability to remain with us in winter when most birds are gone stands him in good stead.

It is readily observed by one who pays the least attention to outdoor life that winter finds us with comparatively few birds. North of Maryland and the Ohio River the robin is practically absent in the winter, except in much diminished numbers close to the border. The bluebird is similarly absent; the great flocks of blackbirds are gone; the bobolink is missing entirely; the thrush and the catbird have all left; the flicker and red-headed woodpecker are also spending their winter in the South. The great mass of our bird population has left us until warmer weather shall bring back to us once more our feathered friends. It is true that we are south to the snowbirds or juncos, and their little slate-colored bodies, with their light breasts and their white on each side of the tail, make our bare hedge rows brighter by their presence. A few of our birds like the song sparrow and the cardinal are hidden away in the thicket, and have not all joined their comrades in the south.

The English sparrow was once probably quite as migratory as any of the rest of these, but a great change has come over his habits. With his newly acquired fondness for the haunts of men he has suffered a change in this respect also. Whatever may have been his reason for migrating, it no longer holds. He now finds himself quite able to stand the cold of winter. Accordingly he never leaves us, except very temporarily. When the migrating season comes the sparrows of the neighborhood are very likely to gather themselves together in a single group and take to the neighboring country. I believe this flocking on their part at this time of the year is a remnant of the old migratory habit. Until snow covers the ground the sparrow is not likely to be seen again in such numbers in the city. The advantage the sparrow gains over his competitors by not going south does not appear during winter. When spring comes, however, his gain is evident. He has his choice of all the nesting sites in the region. When the migratory birds return every first-class place is filled by a sparrow's nest. Nothing but second choice situations remain, and with these the late comers must be content. When we consider how much the safety of the next generation depends upon the security of the young while helpless in the nest, we appreciate what the English sparrow has gained by staying throughout the year. Often while the season is so inclement that it would seem there is still danger of frost, the sparrow builds her nest. All sorts of places are open to her choice. She will find a protected corner under a roof, above a spout, in the corner of the porch, behind an open shutter, in the vines against the side of the house, on top of an old robin's nest in the tree, in the bird boxes which have been put up for more desirable creatures; anywhere and everywhere this industrious little mother is liable to build her nest. Her husband will help her more or less in the task, often bringing material and helping to place it in the negligent pile of which their nest is composed. But he does a good deal more fussing and cheering up than he does actual work, and she seems to depend much upon his cheerful presence for her happiness. It is hard to discourage Madam Sparrow when once she has set her mind on home-making. A bird-lover, some time since, reported how a pair of sparrows had started to build a nest upon his lawn. He, wishing to interfere with the process, took a small rifle and shot the male bird. Within twenty minutes the female, who had scouted round the neighborhood, returned with another mate and resumed her nest-building process. Again he interjected the tragic note into her life by shooting her second husband, only to find her start out in pursuit of a third, with whom she returned in the course of an hour. He felt that by this time he had interfered with her domestic happiness as much as he had any right to do, and suffered her to continue her housekeeping with her third husband without further molestation. I imagine it would have puzzled both birds to tell who was the father of the nestlings who appeared two weeks later.

Not only do sparrows nest early, they nest often. I suggested to one of my students that she locate as early in the season as she could the nest of a pair of English sparrows, which was sufficiently accessible, and that she keep it under observation at intervals of a few days throughout the summer. In the fall she came to me with glowing eyes and gave me her report. "It is simply great," she said. "I never went to that nest a single time this summer to find it empty. When I first got there I found four eggs; after a while these hatched out, and the young were on the nest until they were old enough to fly; but before they had left she had slipped a fresh egg among them, ready to start a new batch. Whenever I saw the nest throughout the entire summer, I found in it either eggs, or young, or both." Such reproductive energy as this is hard to beat; compared with this rate of increase, the ordinary bird is the exponent of race suicide. How can a robin hope to compete with this family industry? What can a bluebird offer that will approach such chances of a worthy successor when his work shall be finished?

These, then, are the most important points in which the English sparrow has varied from his sparrow cousins and made of himself the most successful town dweller in the bird world. He has become clannish and gained the advantages of coÖperation. He has used man's highways and cars by means of which to expand his area. He has cultivated the presence of man and thus gained protection from his enemies, food from man's waste, and nesting sites on man's house. He has assumed a varied diet. The male has become handsome. He has given up migrating, and thus secured the best nesting sites. He has learned to produce many offspring. With all his versatility, why should he not succeed?

Thrown into competition with our native birds, he easily beats them on their own ground. He survives against the competition of birds which seem to us more estimable in every way. The very fact that he survives proclaims his superiority over them, and shows that our criterion is not the one by which nature judges. We like the birds which serve our purpose. We admire the brilliant plumage of the jay, cardinal and goldfinch. We love the mellow notes of the woodthrush, and of the veery, the clear, rollicking outpourings of the bobolink, the musical love song of the brown thrasher, the cheerful scolding of the wren. We are fond of the birds who busy themselves taking the insects out from among our grain and from off our fruit trees. We can only understand the value of the bird to nature when he is valuable to us. So, because the English sparrow does little that is to our advantage and much that is to our annoyance, he is in our estimation a reprobate and an unending nuisance.

All sensible bird-men must clearly acknowledge that he is a very undesirable citizen. I write the above sentence to show that I realize the whole duty of the bird-lover in the matter of the sparrow. This pestiferous creature should be exterminated by traps, by grain soaked in alcohol, or strychnia, by fair means or foul. But personally, I am taking no share in his destruction. Any bird-lover, after reading the foregoing account, can scarcely have missed the undercurrent of my affection for the little rascal. He is a thorough optimist; he is absolutely persistent; no hardship seems to dampen his ardor. His heart is valiant above that of most birds so that he has dared to make of man his near neighbor when other birds consider him their worst enemy. I love him for it. When I am in the midst of a big city with its cliffs of offices and its gorges of paved streets, it is to me a cheer and a delight to see this happy little fellow who has adapted himself to circumstances against which no other bird, excepting the pigeon, can cope. I confess that it would be with regret that I should see him disappear from the landscape. I have missed a long line of spring peas through his ravages, and he has objectionably decorated many places about my own home. But I have yet the first violent hand to lay upon the sparrow, and I doubt whether my hand is ever to be reddened with his blood.

I am going to ask bird-men to forgive me if I say that I believe, although I speak only from general impression, and not from careful research, that the sparrow within the past eight years has reached his equilibrium in the neighborhood of Philadelphia and is growing no more abundant. Meanwhile another and very desirable state of affairs is arising. Bird love and bird protection are so active in this neighborhood that there is growing to be a new race of birds who lack the fear of man their ancestors justly had. Under these conditions the wild birds, which for a while we believed to have been completely driven out by the sparrow, are rapidly returning to our villages and towns, and we have many more robins and catbirds, wrens and flickers than we had ten years ago. We have seen the worst of the English sparrow; he has now found his equilibrium.

CHAPTER IV

Adaptation for the Individual

Among the standard books of the classical curriculum in the denominational college of thirty years ago was a volume which I suppose has practically disappeared from such courses. It delighted many of its students for a reason entirely different from that which the author meant should be its taking feature. It was Paley's "Natural Theology." The author started with a story of a watch found by a savage. This child of nature was supposed to examine its mechanism and to infer that the watch was made for a definite purpose. As I remember, he was even supposed to discover that its purpose was to mark time. It was at least to become clear to his savage mind that this was no chance object, but was the definite product of a designing mind. Having brought this hypothetical savage to these conclusions, the author turned himself to savages nearer home who fail to see design in nature. The book takes up a great many cases of interesting facts in animals and plants as clearly showing evidences of design as did the watch our savage picked up. But the inference we were expected to draw was that the design shown in nature argued clearly for a Designer above nature; in other words, that nature was unintelligible without God. Everyone in the class believed in God without this preliminary, and consequently the book was unnecessary, so far as we were concerned. We started with the condition of mind which the author hoped to produce. One effect the book did have; in the absence of any other reputable course in zoÖlogy, it gave us an astonishing collection of interesting facts about animals.

Some of Paley's statements were certainly peculiar. His Malay pig with its upper teeth wonderfully curved was said to be in the habit of hanging its head upon a bush while it slept, in order to save the strain upon its porcine neck. This was too much even for our credulity. None the less the impression made upon some of us by the evidence for design in nature has never left us.

Among many scientists to-day it is supposed to be crude to speak of purpose in nature, and there is reason for their attitude. But the statement that there is no such plan conveys to the ordinary thinker a meaning that is far more erroneous than could possibly exist in his mind should he believe implicitly in design and purpose. As between design in the universe in the usual sense of the word, and a purely accidental connection of events in the universe, there can be no doubt as to the choice. The truth is far better expressed by the word design than by the chaos which is the alternative idea in the average mind. In these later years we have come to use a different word. We now conjure in such connection with the word adaptation. In every animal and every plant the trained eye sees unending examples of adaptation; that is, of a fittedness to the work it has to do. The modern scientist feels sure not only that the animal is fitted to his work, but that he has been so fitted by the work; that the very use he makes of his organs has determined their structure. This work has decided that the structure which he has is the structure that shall survive and shall produce other structures like itself. Adaptation therefore does not simply express the idea that the animal is adjusted to its surroundings, but it further suggests that the animal by gradual process has become thus adjusted. The word adaptation applies not simply to the result, but also to the process. The scientist does not consider the animal a final and complete result. He thinks it still in a state of flux, and so long as its line lasts it will be in a state of flux. Change is about it on every side, and it must adapt itself to this change or it will pass away. It may adjust itself, as has been previously stated, by moving to another environment in which it feels more at home, but unless it does this, if there come much change in its present surroundings, it must either meet the difficulty by altering itself, or it must give up the struggle. The alteration is unconscious so far as the animal is concerned. It is seriously to be doubted whether there is any recognition of the process on the part of any animal excepting man. But though the process be unconscious, it is none the less there. Slowly and gradually the animal and the environment are becoming adjusted to each other.

While it is exceedingly difficult to lay our hands on any animal which is at present visibly changing its structure, it is not hard to find closely related animals. These are nearly alike in structure in most respects. In a few points, however, they may differ materially, and these points are often directly concerned with different habits of life. Considered in this aspect, these adaptations of a single organ separately examined form an excellent argument in favor of that gradual alteration of the entire organism which evolution suggests.

The most primitive struggle in which an animal can possibly engage is the effort to maintain its own life and vigor. This struggle will result in certain adaptations for the individual, adjustments which make for the safety of the animal himself. These form the subject matter of the present chapter.

The farther up the animal kingdom we pass in the study of adaptation, the more likely we are to find changes which have but little bearing on the safety of the individual. They work for the good of the entire species, sometimes to the distinct disadvantage of the individual. The King Salmon may make its long run to the headwaters of our western rivers, deposit its eggs, have them fertilized, and then float down to death. But it does not die before abundant preparation has been made for the continuance of the race. Such adaptation for the good of the species will be considered in the next chapter.

The first and most important struggle any animal has to enter is the never-ending battle for its food. Occasionally there is a similar straining after the air it breathes. But ordinarily air is sufficiently abundant, except to animals living in the water, where the supply is always more or less restricted and easily becomes exhausted. But food is the constant need of every organism, and most creatures die for lack of it. In this struggle the animal is pitted against those of his own kind, rather than against those of other species. Even his brother is his enemy, for he desires the same food. In many a nest of birdlings one of them fails to reach its development simply because the parent either is unable to find or it cannot carry enough food to satisfy all the hungry mouths in the same nest. Before the nestlings are ready to take their place in the struggle for life outside and hunt their own living, one or more of them has succumbed.

After the battle for food comes the struggle for shelter. For most animals there is no such thing as shelter. They are exposed to the inclemencies of the weather and to the depredations of their enemies without the means of retiring into any situation which might protect them. In the higher animals, especially when they are warmer blooded and their bodies must be kept at a higher temperature, some form of covering has come to be almost universal.

Though comparatively few animals are prepared to seek shelter from the cold, all of them have enemies against whom they must battle. These foes may wish to eat them or may simply wish to get them out of the way. In either event this struggle is so persistent and so keen that after starvation it is probably the source of the largest loss to the animal kingdom.

Considering first the feeding habits of animals, we find they are exceedingly varied. Some creatures simply engulf other and more minute animals, often only microscopic in size, in such quantities as to satisfy their hunger. Others, feeding upon larger plants or animals, must have some means of breaking off particles of this food; still others confine themselves entirely to nutritious fluids, and must have organs adapted to this particular type of food.Insects are so common that anyone, who cares to, may easily verify what is here described. It will take nothing but a clear observant eye and a little patience to make out what is suggested. Each of our common insects has one of two clearly defined habits in the matter of food. Either it eats solid food, which must be made fine before it can be taken into the mouth, or it feeds upon liquids. These liquids may be easily accessible like the nectar of flowers, in which case one sort of mouth will serve; or they may be the juices inside the tissues of animals and plants, when an entirely different type of mouth must be employed in their acquisition. Perhaps the most easily found representative of the biting type of mouth, which breaks up solid food, will be seen in the common grasshopper. Doubtless each one of my readers has at some time taken a grasshopper into his hand, and, holding the tip of his finger against the insect's mouth, has promised the creature its freedom on condition that it disclosed its reprehensible habit of chewing tobacco. The grasshopper surely complied, and I trust the promiser was as good as his word. The grasshopper's head is so placed that, while it is at the front of its body, the mouth is directly on the under side of its head, while the eyes are at the top of the front of its face. Under these circumstances it cannot see what is going into its mouth, and this makes an interesting variation of conditions to which it must adapt itself. The means by which it accomplishes this will be clearer if the mouth of the grasshopper be compared with our own. Our lips are upper and lower, but the grasshopper has a front lip and a hind one. The broad front lip is easily seen at the forward side of the mouth. Just behind it, serving the purpose of our teeth, is a pair of hard jaws with horny tips upon them, which serve to break small pieces from its food. While our jaws and those of all other backboned animals work up and down, so that we may be said to have an upper and lower jaw, the grasshopper and all of his insect, crab, or spider relations, which have jaws at all, have them right and left, and they work from side to side. Behind these harder mouth parts is found a pair of softer jaws, each of which has on it a little finger-like feeler. With this pair the insect holds its food while the hard jaws break it to pieces. The hind lip follows, and is also provided with short finger-like feelers. The feelers on the hind lip and on the soft jaw are necessary because the eyes are so placed as not to be able to see what goes into the mouth, hence the insect must make up for the loss of sight by the addition of touch. The same type of mouth as the grasshopper has will be found among the beetles. Here the males sometimes have the hard jaws so enormously enlarged that they are known as pinchers and have given to their owners the name of pinching bugs. All insects with such jaws as these use them for breaking up solid food.

A glimpse at the mouth of the butterfly captured on an adjoining flower will show a most remarkable variation from that seen in the grasshopper. Practically all of the mouth parts mentioned are present in this insect, and its early ancestors had their organs practically like those of the grasshopper. Now they are so modified and united with each other as to be almost unrecognizable. The pair of soft jaws has become very much elongated, and they lock together in such a way as to enclose a hollow space between them through which the creature can suck its fluid food. Not only have these soft jaws joined together, but, because they have become so much elongated when not in use, they must be coiled up like a watch spring and laid between two hairy lip-like processes which correspond in reality to the two finger-like feelers of the grasshopper's hind lips.

The butterfly, lighting upon the corolla of the flower, uncurls this long "tongue," and through its hollow center pumps up into its crop the nectar which the flower has stored in its base. When the butterfly comes to get the nectar from the flower, it rubs upon its own hairy body pollen from the stamens of the flower and carries it to the pistil of the next flower of the same kind which it visits. Most of us have at some time sucked the nectar from the back of a torn honeysuckle blossom and approved the taste of the butterfly in this matter. If the airy creature be watched as it lights upon a flower, it will not be difficult to see it uncurl this long tongue and probe the depths of the flower. If the butterfly be taken in the hand and the tip of a pin inserted in the center of the coiled tongue, it can be uncoiled without the slightest harm to the butterfly.

Insects which wish to use for their food the juices of other animals or of plants do not find them so easy to gather. In the mosquito most of the mouth parts are developed into slender pointed bristles wrapped in a hind lip. These bristles serve to puncture the skin of the creature attacked, while the curled lip serves as a tube through which the blood may be extracted.

If, while sitting on the porch on a warm summer evening, mosquitoes begin to annoy, let one of them at least serve to show his method of procedure before he is destroyed. Allow the creature to alight upon the back of your hand and slowly raise the arm until the eye looking at near range can see the head of the mosquito, which, by the way, is sure to be a female. Males in this species are entirely harmless. They never eat after they have grown up; that is, after they are truly mosquitoes. But the female is very assiduous. Alternately raising and lowering her lancets from either side, she pierces, then saws, her way down through the flesh until she has buried her instruments in her victim and her head rests against her prey. Now a pumping motion of the abdomen will be apparent, and this continues its accordion-like action until it becomes more and more distended. The insect only gives up its task when the entire abdomen is swollen into a great red ball of blood. The mosquito will now slowly withdraw its instruments and retire from the scene, if permitted to do so. If there is any fear of annoyance from the bite, a drop of ammonia immediately applied will counteract any irritation which would have been produced by the saliva of the mosquito. The insect is not intentionally vicious in this procedure. It is simply gathering its own natural food, though this does not make it less annoying to us since we are its victims. The swelling produced after the bite is the result of the action of the saliva the mosquito injected into the wound. The opening through the tongue is so small that blood would readily clot inside the tube and prevent its further usefulness, did not the mosquito inject the secretion of its salivary glands into the wound. This acts upon the blood in such a way as to prevent its coagulation.

Anyone who thinks carefully can add numberless specializations for food getting. For instance, primitive mammals have little pointed teeth which fit them for feeding on insects. In each of the great order of mammals a special development of these teeth has occurred. Among the rodents or gnawing animals the front teeth have become long and chisel-shaped for nibbling. The horse has formed them for nipping, and his hind teeth for grinding. In the dog the teeth near the front have become long for tearing his flesh food, while his hind teeth, working with the motion of scissors, cut it into pieces.

A second great class of specialization is seen in the changes of habit that provide the animal with shelter. The home seems so necessary a part of human life that it is almost impossible to think of an animal having nothing that in the faintest degree could be called a home. We at least expect it to have some sheltered place in which it passes most of its time and to which it returns after its wanderings. The great majority of all animals have no such home. The place in which we find them to-day may not be the place in which they will be to-morrow. All places are alike to them. The ordinary conduct of their daily life drives them about in the search for food. Their attempt to escape from their enemies leads them each day into new situations, and they may, and probably do, have no power to recognize the old location if they return to it. When we come to the backboned animals there is a little more tendency to a stationary location. The sun fish may frequent the same reach of the stream, the trout may haunt the same pool, year after year, but a great majority of fishes doubtless move indiscriminately up and down the stream or about the lake or ocean and are not found two successive days in the same place. The same may be said of frogs. For a time a particular frog may have a fondness for a special bend in the stream, but it is only a temporary fondness, I believe.

Our own need for shelter is the prime motive in leading us to build a home, and this necessity arises first of all because of our warm blood. What we are accustomed to call cold-blooded animals are not truly so. Their blood holds practically the temperature of their surroundings. As the air or the water in which they live grows warmer or colder the bodies of these creatures alter with it. Consequently they are active when the temperature is high and grow more sluggish as the thermometer falls. When the day grows distinctly cold the animals may go practically dormant.

Only the birds and mammals have warm blood, and of these the birds are distinctly the warmer. Whereas the temperature of the mammals runs from about ninety-eight to a hundred degrees Fahrenheit, that of birds lies somewhere between one hundred and five degrees and a hundred and ten. Creatures which are warmer than their surroundings must have some protection against chilling. Accordingly both mammals and birds have clothing. In the case of mammals the covering is fur, in the case of birds feathers. In some of the tropical animals like the elephant and rhinoceros, or in man, who has learned to protect himself in cold regions by making clothing for himself, this hair is very short, and except where serving for ornament is quite scanty, no longer being of use as a protection. But the great majority of all mammals are well covered with a dense coat of hair. In many of those living in the colder regions there is in reality a double coat. The fur seal of the Alaskan Islands is so provided. A set of long hairs deeply fastened in the skin forms a covering, which shows on looking at the seal. Underneath this layer, and set but lightly into the skin, is a short coat of very much finer hair known as the underpelt. When the skin is taken from the seal it is split by machinery into a lower and an upper layer. When so split the deep-seated pits of the long hairs are cut, and these hairs come out. The fine underpelt thus laid bare is what is commonly known as sealskin. Fashion has decreed that this must be dyed a rich brown, although when taken from the animal it is nearly mouse gray.The birds have need for better clothing. To begin with, their blood is much warmer, and hence needs better protection from outside cold. In addition such of them as fly high must be prepared to stand great variations in temperature. For these purposes birds need a covering of the finest type. This clothing, in addition, must be extremely light because the creature must carry it into the air in flight. All of the requisite conditions are thoroughly met by the feather, which is the lightest and warmest clothing known to man. If at night we wish, regardless of expense, to keep ourselves warm with the lightest and warmest of covering, we send to the Arctic Sea, and from the breast of the eider duck we pluck the down which lies between the warm blood of the duck with its temperature of one hundred and seven degrees and the water in which the iceberg floats.

Young mammals and birds, before their clothing has well formed, are naturally susceptible to cold; this leads to the first genuine approach to a home among animals lower than man. Birds lay their eggs long before the creatures inside of them are ready to emerge. Accordingly they have learned to build nests in which to place these eggs, and to protect them from the outside air; meanwhile the bird keeps the eggs warm by close contact with its own body. The lowest of the birds may lay their eggs simply on the ground without any special protection. As we rise in the scale of the bird world we find nests provided for the eggs. These nests become increasingly complex and specialized, until we reach the oriole's home with its wonderfully woven mass of fiber, which, in spite of its apparent looseness, supports well the weight of the mother bird and of her eggs. The robin, not content with making a woven basket, plasters it with clay, and makes an absolutely impervious nest.

When we remember that both mammals and birds are the modern descendants of cold and scaly reptiles of an earlier geological time, it becomes interesting to compare their clothing. Evidently in the mammals hairs began to come out between the scales. Gradually the scales became fewer and the hairs more abundant until finally the scales have all disappeared, except those that remain as the claws on the toes. The ancestors of the birds, on the other hand, boldly transformed their scales into feathers.

Another need for shelter arises in connection with the approach of winter. This problem of withstanding the cold season is complicated by the presence of two new factors. First and most directly, the cold itself is a distinct obstacle to the comfort of many of these creatures; as a secondary result of this cold, the food of many animals disappears entirely in winter. Most of our birds meet this difficulty by changing their base of operations. When the north grows cold these creatures fly to the south. Some of their migrations cover enormous stretches of country. Our bobolink, so well known and loved by all watchers of spring migrations, passes twice a year between the latitude of New York and Rio Janeiro. One of our most careful students of bird migration says that the Golden Plover makes, twice each year, the long journey from the Arctic shores of North America to the plains of La Plata.

Different fur-covered animals have specialized to meet the winter by any one of three different methods. They may brave it out, hunting for their food as best they can all winter long. Such a course is pursued by the rabbit. Again like the squirrel, they may store large quantities of food during the summer, and on this provender they may subsist during winter, remaining for most of the time near their hiding-places, which, however, they may frequently leave upon warm days. A third method is less common, but very interesting. The groundhog or woodchuck is the best-known example of the group. It remains asleep, or, as it is technically known, dormant, during the winter. This stupor is more profound than ordinary sleep, and from it these animals awaken with difficulty. It is needless to remark that the groundhog's behavior on the second of February has no relation whatever to the weather we are to have later in the season. This is coming to be pretty generally understood. While the newspapers each year comment upon the groundhog and his shadow upon that day, year by year the notice has more of humor in it, and fewer people pay any attention to it.

As for the backboned animals which are cold-blooded, these must, unless they are fish, give up the struggle completely, bury themselves in out-of-the-way places, and go worse than dormant. They often become absolutely cold and stiff. In the case at least of fish, it is quite possible for them to be frozen stiff, even to be enclosed in cakes of ice, and still to recover if the encasement is not too long continued. But the snakes, the turtles, the toads, the lizards, all are hidden beneath the ground waiting in absolutely unconscious rest the return of warmer weather.

After the need for food and shelter comes the continually recurring necessity on the part of almost every type of animal to escape from the unwearying persecution of higher creatures which would feed upon it. The whole creation is a constant network of animals which prey upon each other. It is the fate of a great majority of all creatures to fall victim to other animals to whom they serve as food. Accordingly nature has concocted many devices by which she assists her favored children in escaping this relentless persecution. Perhaps the most widespread means which animals have developed in order to elude their enemies lies in the possession of power to escape their attention. Two different factors may contribute to this end. The first of these consists in the practice on the part of many animals of remaining absolutely quiet in time of danger. This instinct seems to be nearly universal. The first impulse of most animals upon discovering danger is to remain absolutely motionless. The eye detects, with ease, objects in motion. These same objects might entirely escape attention were they quiet. A mouse could remain in the corner of a room for a long time without attracting the eyes of the occupants of the room. Let it but scamper across the corner, and at once it is discovered. It is quite conceivable that early animals were divided in the matter; that the impulse of some was to escape from danger, while others, frightened by the presence of the enemy, remained absolutely still. Each plan has succeeded. Those which, on running, ran fast enough to escape became the parents of others like themselves, led eventually to a line of animals in whose speed lay their safety. Those, however, which attempted to escape, and failed because they were not swift enough, had their line cut off, and were thus less likely to be represented in the following generation. The constant result of errors along this line would be to destroy the slow and preserve the swift, and in the course of time it is quite thinkable that only the swift should remain. As the movements grew more and more keen, even the slower of these would pass out, thus tending always to produce the succeeding generation from those who were most rapid, and hence most likely to transfer to their children a similar power.

But there is another tendency of animals which leads them when frightened by their enemies to remain quiet. If this impulse is obeyed thoroughly enough, it is easy to see how the owner of this habit might entirely escape detection by his enemy. Any restless animal unable to restrain his nervous agitation naturally betrays his presence and is picked off. The result of evolution along this line would be the exact reverse of the preceding. Those that lay most absolutely quiet would be the parents of succeeding generations, while those who were slow in coming to rest, or were indifferent about remaining quiet, were picked off, and their tendency eliminated from the future of the species. In this way many animals have come to keep entirely quiet in the presence of danger. It is not a sign of high intelligence. As a matter of fact, it is rather a stupid procedure, so far as the animal itself is concerned, but it is a preserving stupidity, and many animals have it.

The "June Bug" (which is not a bug, but a beetle, and arrives in May) has this interesting habit of keeping quiet. If in its flight it strikes the globe of an electric light, it falls at once to the ground, and remains perfectly quiet for a time. After a short interval it recovers and starts out to regain its previous activity. But this recovery is by slow stages, and the whole procedure on its part looks exceedingly stupid.

The little snake with flattened and expanded head, known as the blowing viper, or puff adder, is one of the most amusing representatives of the tendency to "play dead" that could well be found. If you strike him the faintest blow with the lightest stick, he at once goes into apparent convulsions, in which he seems to suffer the greatest agony. Then, throwing himself upon his back, he, to all appearances, yields up the ghost. If, however, you retire but a slight distance and keep your eye upon him, you find that his ghost returns after a comparatively short absence, and he slinks away out of danger. This is the most effective exhibition of this kind with which I am acquainted.

As for the habit of "playing 'possum" on the part of our opossum, the trick would seem to be particularly inane. The truth of the matter is, what is attributed to an unusual brilliancy on the part of the creature is positively unusual witlessness. The animal has an exceedingly small brain, as compared with that of a dog of similar size, and to anyone who knows brains at all this particular organ would not be looked upon as furnishing its owner much ability. The fact is that the opossum has exceedingly small wit, and this little deserts it in an emergency, as a result of which he grows helpless and motionless. This is often supposed to indicate great wisdom. There may be wisdom in it, but it is the wisdom that lies back of all nature. It certainly is not the wisdom of the opossum.

Man himself possesses to a marked degree this impulse to keep quiet in danger. The man from the country who is visiting the large city, suddenly startled by the "honk" of the auto horn, finds his power of movement promptly arrested, and he is not unlikely to be struck and injured by the machine from which the city dweller would easily escape. This is not particularly to the credit of the city dweller, who, when in the country, may find himself similarly startled by the sudden appearance of the calf, the pig, or the sheep. The bull, which a country boy, accustomed to him from childhood, will drive with a willow switch, is a source of terrified concern to the city man.

While the trick of keeping quiet serves many an animal in time of danger, there is another device for escaping attention, far more common and widespread throughout the animal world. The eye does not easily see an object if it is colored like the background against which it stands. A host of animals find their main safety in being indistinguishable in color from the surface on which they live. There are many biologists who seriously question whether protective coloration, as Darwin called it, is as effective as he believed it. In some quarters it is the present fashion to doubt protective coloration entirely. No one has yet shown any principles which will better explain the great color scheme of the animal world, and until such explanation is forthcoming I believe it will not be wise for us to discard the idea of protective coloration. No doubt it has been overworked by enthusiastic believers in its efficiency. At the same time, to overlook it completely, is, I believe, to make a greater error. I have little doubt that when the broader explanation comes, which will satisfactorily explain the color scheme of the animal world, the idea of protective coloration will be found, not so much to have been wrong, as to have been but partial. It will be included under the broader principle which takes its place and will not be supplanted by it.

The idea of protective coloration is that very many animals have ordinarily come to be colored like the background on which they live. The process has taken many generations, and is very slow, but is none the less sure in the end. In most cases the animal is probably entirely unconscious of this point in its favor, and usually it does nothing to assist the deception. The result is none the less effective because the animals themselves are unconscious of the process. The cabbage worm is green in color like the cabbage. This does not mean that it got green by eating cabbage or by longing for greennesses. Through long years the enemies of the cabbage worm have been picking it off the plants on which it fed. This does not imply that cabbages as we know them are very old, but cabbage worms doubtless ate the leaves of the sea-kale long before man had cultivated it into cabbage. During all these years the enemies of the caterpillars, generally in the shape of birds, have been assiduously gathering them up.

When we see how much the various members of the same human family may differ in complexion, how much the various pigs in the same litter may differ in size and in coloration, it is easy to understand that among these caterpillars which have eaten the cabbage there must have been considerable color variations. I do not imagine for a moment that the birds had any preference for any particular color in their cabbage worms. They took every caterpillar they saw, but they naturally first saw those that were least like the background on which they lived. The only caterpillar which was effectively hidden from his enemy was the one that was indistinguishable on the leaf. If it escaped in this way, the probabilities are that it would produce young which would be at least a little more likely to be green in color than the progeny of its darker-colored brothers and sisters. By this continued process the birds steadily weed out the darker-colored specimens. There would result, in the course of time, a race of caterpillars, whose ancestors for so many generations back had been light green in color, that there is little likelihood of any of the older and darker forms turning up again. In the course of time all dark tendencies will have disappeared from the family and practically all of the group will be light green. Any sport or variation in the shape of greater conspicuousness would fall a quick prey to the enemy and its line be cut off forever.

The same sort of activity has resulted in the peculiar green color of the katydid. This creature lives chiefly upon the leaves of trees and shrubs. This insect is so large that, even though it is leaflike in color, it might still be conspicuous. As a result those katydids whose wings were most like leaves in form were least likely to be picked up by the passing bird. This sort of protective appearance is intensified by exactly the same means as that which brought about protective coloration. The katydid least leaflike in appearance was eaten first. Thus those most leaflike remain until the last, and are most likely to produce young. Again, it was not the fact that they lived among leaves which made them look leaflike, but it is because they look like leaves that they escaped being devoured.

The katydid has materially assisted in its own preservation by being active chiefly at night. In the daytime it keeps comparatively quiet. Thus seated upon a twig, especially if hidden among the leaves, it is almost unnoticeable. At night, however, it moves about more freely, seeking its food and eventually its mate. At such times it becomes distinctly more conspicuous because its wings are steadily fluttering. The hind wings are filmy and are very light green. The creature looks most ghost-like as it flies through the evening air.

A very similar history lies back of the coloring of the ordinary toad. Though descended from the frog, and originally a creature of the water, the toad has long since adapted itself to live upon the dry ground. It still produces its young in the water as it did when a frog. Whereas the childhood of the frog, that is, its tadpole stage, is very long and it assumes its adult form comparatively late, just the reverse is the case of the toad. The young hasten through their tadpole stage within a few weeks, and assume the shape of the parent toad when about big enough to cover your little fingernail. Now they leave the water and seek dry land. Naturally they make the change when the land is damp, that is, after a warm spring rain. People seeing these multitudes of little toads hopping around over a bare spot of ground, and remembering the rain of the night before, insist that it has rained toads. Of course it never rains down anything which cannot evaporate up. The stories of showers of toads and of earth worms, with an occasional fish, or even creatures of larger size, are all pure myths. There are conceivable tornadoes after which there might be a shower of such creatures, but at such a time it is likely also to rain barn roofs and buggies. You may be sure that toads which come down in the rain are dead after they strike the ground.

The little toads started out, perhaps a hundred at a time, from the small pool in which their eggs were laid. These creatures find dragons on every side. The gartersnake comes along and gets his first toll; the heron follows him and takes such as catch his hungry eye; the turkey gobbles up his from what are left. By the time the toad-eating creatures in the neighborhood have taken such as they found, there are very few remaining. These doubtless have been left for a very good reason, generally because they were not noticed. This was because they looked like the ground on which they sat, and because they kept perfectly quiet while the enemy moved about. This process has gone on so long that the toad has come to be astonishingly well protected by its resemblance to the ground. This likeness it intensifies by its interesting habit not only of keeping entirely quiet, but of dropping its nose to the ground, instead of sitting high on its front legs, as it does when not in danger.

I have noticed that if a snake and a toad be placed in the same cage, when the snake approaches to capture the toad the toad drops into a squatting position, and is very likely to blow himself up until he is rounder in outline than he was before. Whether this is a deceptive trick which makes him the more resemble a stone is more than I can say. I do not remember having seen our eastern toad do it. I have seen it happen a number of times in the laboratory of a Colorado naturalist, and it is quite possible that in the open country more sparsely covered with vegetation than is our ground in the east this inflating device may serve the toad more effectually than if it kept its own outline.

Even among creatures far more active than the toad and the katydid an inconspicuous color must certainly result in distinctly better protection. Everyone knows the jay and the cardinal when first he has seen them, if only he has a slight acquaintance with their pictures. They are so conspicuous that we recognize them at once. More common in my region than the jay or the cardinal is the red-eyed vireo. This creature moves industriously in and out among the leaves of our trees. It is persistently in motion, is nearly constant in song, and is a bird of fair size, being larger than our English sparrow, though smaller than a robin. Many a nature lover will recognize twenty-five or thirty birds at sight without any difficulty, and not know the vireo. Yet the vireo is more common than two-thirds of the birds he knows. There can be but one reason for this; the bird is inconspicuous. The olive-green of its back, with its light under parts, serves to hide it completely amid the foliage. Even the bird-lover learns to find it first by its jerky song, and then by watching for its movements among the leaves.

One aspect of protective coloration has been brought to our attention by the artist, Mr. Abbott N. Thayer. He first clearly explained why it is that animals are usually so much lighter on the under side than they are upon the upper. Mr. Thayer proves his position by taking some ordinary cobblestones and painting one of them a uniform color and placing it upon a board painted the same color. One would think the stone would be inconspicuous; as a matter of fact, is quite easily seen. The underside of the stone, turned away from the light, is so shaded as to mark a distinct boundary between the stone and the board. Another cobblestone was colored on its upper side like the board, but the color faded into a lighter and lighter tint until the bottom of the stone was nearly white. This stone, placed upon the board, was at a short distance nearly invisible. In other words, although the pigment was actually lighter on the under side, it was so much less intensely illuminated, that the result was the same in tint as the other side under the clear sharp light of the sky.

Many a person, looking down into the water from a bridge, sees nothing whatever of the fish in the water below, because their backs are exactly like the bottom of the stream. Suddenly one of the fish, by a quick movement, turns its lighter under side over in such a way that it is clearly illuminated from the sky. Immediately a flash as of silver strikes the eye of the onlooker and makes him aware of the presence of the fish which had previously been undetected. If rendered thus suspicious, the observer will carefully examine the bottom of the water, he may quite likely find dozens of fish which had previously escaped his attention.

Nature is very versatile. So many of her apparently chance ventures have proved successful that she has retained many devices by which her children may be safe. One of these, which is doubtless often quite effective and may serve to save an animal's life, is that of being able to emit an odor so nauseating as to offend the enemy's sense of smell, and doubtless remove the keen edge of his appetite. It is not uncommon among the group of insects properly known as bugs to possess an exceedingly unpleasant odor. Anyone who has handled a squash bug will know exactly what I mean, and there are other members of the group not so common as the squash bug, which, at least to the human nose, are distinctly offensive. Some of the beetles also save themselves by this device.

One of the most interesting developments of this peculiarity is found in the case of the common skunk. This creature has in each groin a gland capable of secreting a highly offensive fluid. Ordinarily this liquid is kept safely within its sac, and for a long time none of it may escape. When closely cornered, the skunk will turn its tail toward the enemy and with a quiver and a flip of his tail it can guide the openings of two little tubes that come out along the root of the tail in such fashion as to eject the fluid in a fine and foul-smelling stream against the animal from which the skunk would escape. Once fairly hit by this fluid, I imagine most animals will drop the skunk. A dog surely will, and will hate himself for having made the attempt to capture anything which must be so ignominiously allowed to escape. If ones clothing is well saturated with it, it is nearly useless to hope to remove the odor. A dog will carry the smell for several weeks. For a long time it will be so strong as to make him an unfit denizen of the house. Even swimming in deep water does not remove it. After two weeks, although he may seem to be practically free from the odor, a light rain will bring it all out again and make him nearly as offensive as before.

Not as prompt in its action, but in the end nearly as effective, is the protective device which the toad sometimes uses to his distinct advantage. May I be pardoned a personal account of this particular feature. It was my good fortune to be for a short time a student in a class taught by Edward Drinker Cope, one of the most brilliant of our American biologists. Prof. Cope mentioned in class the fact that the Batrachians (the group to which the toad belongs) have in many cases the power to emit from their skin a fluid which is sufficiently nauseous to deter an animal from eating the creature that secretes it. Upon such authority as this, I had no hesitancy whatever in repeating Cope's statement. One morning I had a class in the field studying the ground ivy, whose dainty blue flowers were lifting themselves out of the dewy grass. While we were thus engaged, a toad joined the circle. He came out of his dewy retreat clean and fresh from his morning bath. I took him in my hands, and made him the subject of an immediate lesson. I showed to my pupils his eyes and his interesting method of handling them, his tongue and its strange insertion; showed them how to look into his mouth and look up his ears to his ear drums, and pointed out many other interesting facts. Then I told them how Cope had said that the toad had power to emit from its skin a fluid so nauseous that many an animal hesitates to eat it. This is the first peculiarity I had mentioned which I had not myself observed, and a scientific qualm came over my conscience. Why had I never verified this statement which I had so frequently repeated? On the impulse of the moment, with the bright, clean skin of the creature fresh from the dewy grass, making it less than usually repulsive, I ran my tongue up its back only to find that it had no taste whatever. I was of course surprised, but I was not foolish enough to deny, as the result of one observation, the statement of a good scientist. The observation, moreover, was one which I naturally did not care to repeat with any frequency. Of one thing I was sure, toads do not always have an unpleasant taste.

A year later I had a class down by the side of a neighboring pond. The pool was not an attractive one, and I had picked from it a more than commonly unappetizing looking toad, which proved to be a mother which had not yet laid her eggs. As I held her in my hands and exhibited her various points to my pupils, I told them of Prof. Cope's statement. I also told them of my unsuccessful attempt the previous year to verify the statement. I added, however, that I would not repeat this experiment on this unappetizing specimen. Hereupon the toad not only exuded, but squirted, from a gland over her left shoulder blade a fluid, milky-like in appearance, and forming a jet as thin as a needle, but ejected with force enough to strike my face, which was at least fifteen inches away. I moistened my finger on my tongue, lifted the fluid from my cheek, and tasted it. Cope was right. A toad can exude a most nauseous fluid. Horsechestnuts extracted and distilled might possibly provide something as bitter. Why did I not find this in the preceding case? I have too few observations on which to base a conclusion, but I have a suspicion as to the reason. In the case of the toad which spurted the fluid in my face, we had a creature with whose life were tied up the lives of her many offspring, to be produced from the eggs she was so soon to lay. Under conditions like these, nature is more than commonly careful of her children. Whether this be the reason or not, toads do not always have an unpleasant taste, but when they do it certainly is most unpleasant.

There remains to be considered the most effective plan yet mentioned of escaping the enemy, and that is of really escaping. In all the devices we have considered thus far the enemy is eluded. When the creature lies quiet, or finds safety in its protective coloration, or in its bad taste, or unpleasant odor, it still remains in the presence of the enemy. A more progressive plan altogether is to escape the enemy by flight. The great advantage of this plan lies in the fact that the acquisition is valuable for every purpose. The creature then can escape the enemy, can range widely for food or for a mate. This gives it an enormous advantage in the struggle for life. The power to fly, in insects, was doubtless originally gained in the attempt to escape the enemy. Among many of the lower animals it is nearly the only purpose that flying serves. Later on it enables the animal to pass from one food locality to another. In a few creatures it plays an effective part during the mating season. These last are probably both derived powers, and the original function was that of escape from the enemy. The grasshopper has grown its long legs to serve him for safety, and through them it is helped along, moving about chiefly by leaps when it wishes to go any material distance. It is only toward the very end of its life that the grasshopper has wings, and then they serve probably to aid in the search for a mate. Among the birds flight began simply in sailing out of the trees, into which the creature, still half lizard, had crept to escape its enemy. The earliest bird known to us had comparatively insignificant wings. There was really more support in its tail than in its wings, and this would distinctly indicate that it glided more than it flew. It had claws also upon its wings, and it was probably the case that this creature crept into the trees, at least in its earliest forms, and sailed down in a manner not unlike that employed to-day by the flying squirrel. From such simple beginnings came the wonderful power of flight in the birds.

Among mammals the attempt to escape from the enemy has led to an interesting development, which will be more fully explained in a later section when we speak of the history of the horse. The early mammals walked flat-footed, as we do on our feet and as the raccoon and the bear do on theirs. Gradually, however, as their enemies became more fierce and better able to injure the larger mammals, the latter gained in power of flight, and this gain consisted first in rising from the toes, lifting the heels completely off the ground. At the same time the leg and foot were gradually lengthened. Doubtless in this way the fleet animals, like the deer, the horse and the giraffe, first came by their long legs. Constant elimination of the short-legged ones, by the pursuing enemy, resulted in the selection of the long-limbed ones for breeding purposes, and hence to the ultimate elongation of the legs of the species.

The method of escape from the enemy involves cowardice. "He who fights and runs away may live to fight another day," and so it may be the part of wisdom in the weak creature to escape from his enemy by flight. It is a far more estimable process, from our standpoint at least, to stand against the onslaught of the enemy and beat him upon his own ground. This end is secured in many animals by acquiring horns or by lengthening certain of the teeth. The horn is a very ancient instrument of defense. When the reptiles ruled the land horns were not uncommon. They consisted in those days of hardened scales, which lengthened and fastened themselves over a core of bone. Such an old-fashioned instrument, sometimes made of newer materials, still remains the defense of a number of animals. The rhinoceros has upon his nose a lengthened projection, which is what might not improperly be called hair glued into a cone. This enormous horn is a frightful weapon, both of offense and defense, and, when backed by the terrible weight of the body of the rhinoceros, it can do as deadly work as almost any instrument of destruction known to animals below the grade of man. But, after all, this is an old-fashioned method, and the rhinoceros is a relic.

Among the carnivorous animals the teeth, which were developed first chiefly for the tearing of flesh in its consumption, became effective for their courageous owners. Because these tearing teeth are well developed in the dog they have come to be known as canine teeth. Usually where an animal can use its teeth effectively for offense or defense, it is the canine teeth that are thus modified. The cat has developed them better than the dog, and one of the cats of a bygone geological period had canine teeth so magnificently enlarged and so sharp at the back as to give this frightful creature the name of the saber-toothed tiger. The long teeth in the upper jaws of the elephant, commonly known as tusks, are not canine teeth. The elephant has completely lost his canines. His tusks are his incisors, and they have developed as have almost no other teeth in the mammals.

These are only a few of the numberless devices nature has evolved for furthering the success of her children. There are so many others that to many of us they form almost the chief point of interest in our study of a new animal, or our closer observation of an old friend.

CHAPTER V

Adaptation for the Species

The strife, as we have described it thus far, is a purely selfish struggle. Every point gained is a point favorable to the welfare of the individual animal. But nature is uncommonly careless of the individual unless the advantage gained is also of use to the species as a whole. Very often the life of an animal ceases when provision has been made for its young. The male garden spider may have a long and dangerous courtship, in which the uncertain temper of his ladylove may lead her to bite off four or five of his eight legs. But her ingratitude is not yet complete. He may have barely accomplished his desperate purpose of fertilizing her eggs at all hazards, when she ends the process by eating him. The male bumblebee fertilizes the female in the late summer and then dies. She does not lay her eggs before the next season. So it happens that no bumblebee ever sees its own father, and no father bumblebee ever sees his own children. In the honey bee the male, which has been fortunate enough to fertilize the queen, pays for his honor by death within the hour. Superfluous bachelors, among the honey bees, when the bridal season has passed, are driven from the hive to die of starvation.

An animal need not always be successful himself, but it is more essential that he hand down his successful traits to those who come after him. It is more important for the future generation that an animal should have had it in him to do great things, though he himself really have never done them, than that he should have learned to do great things on a meager original endowment. Not what an animal accomplishes is important to his children, but what he has it in him to accomplish. Accordingly Nature is full of devices by which those who have proved their original endowment by winning out in the struggle shall hand on this endowment to a subsequent generation. In other words, Nature is anxious that they may successfully mate. Here we are again on distinctly debatable ground. Darwin himself believed thoroughly in what he called sexual selection. It is the essence of this idea that the males and females have grown unlike, more technically have developed secondary sexual characters, through the choice of the mating pair. It would usually be the more serious loss if accident should come to the female, for she may carry fertilized eggs for some time. Hence, if both sexes may not become attractive, it is usually the male that develops fine colors, ornamental appendages or a captivating voice.

An interesting reversal of this process has taken place in civilized man. His more savage ancestor adorned himself more lavishly than he permitted his mate to do. With the advance of civilization man has undertaken to defend his own mate most valorously. The result is it is safe for her to be beautiful. Under these circumstances, however, it is more necessary to her welfare that her consort be vigorous rather than that he be handsome. Hence in the human species beauty has become the prerogative of the woman, and this is increasingly the case the higher the civilization. Whether woman suffrage and self-support will reverse this process remains to be seen. There are indications that point that way.

There are many biologists who are at present expressing serious doubt as to the validity of sexual selection. As in the previous cases of protective coloration, I believe it will be wise for us to retain, even though with an interrogation point behind it, the idea of sexual selection until such time as those who object to it have furnished us with another theory which will more nearly account for the observed facts. While entirely conscious of the possibility that there is a weak spot in the theory, we will still tentatively hold to sexual selection. The fact that beauty in women is so intensely attractive to man, and that vigor and manliness in man are so attractive to women, leads us to infer that among the lower animals, although of course in a vastly less degree, vigor and beauty are also attractive. The weakest point of the position lies in the fact that it probably presupposes a higher degree of capacity for appreciation on the part of lower animals than they possess. Those who deny the truth of the theory laugh at the idea that a butterfly can see clearly enough and care enough for what it sees to notice whether its mate has wings of one type or of another. The size, number and position of the spots on the wings of many butterflies are so nearly constant that they cannot of themselves have been entirely determined by the choice of the insect. Yet this may not preclude the possibility of the fact that, while the spots were produced through some other agency, certain types of them were selected by sexual preference.

If attractive coloration is effective anywhere in the animal world, it will possibly be found among the insects, but it is especially likely to be found among the birds. Very many field workers in these groups feel quite sure of the value of attractiveness. When butterflies chase each other up and down, circling and doubling, following each other for long distances, it would certainly seem as if they were pleased with each other's appearance. Some naturalists, especially those who have worked chiefly in the laboratory, insist that it is the odor, not the color of these insects, which is attractive, and some experiments which have been made would seem to point in this direction. But the creatures experimented upon most carefully were night-flying moths, and it is quite possible that the sense of sight in the night-flying moths has lost its vigor.

The great difficulty in understanding sexual attraction in insects, as based upon beauty, lies in the undoubtedly lower development of their nervous activity; in other words, in the apparent absence of anything worth calling mind. I think no one imagines that a butterfly, looking upon two other butterflies who are competing for her affections, deliberates between them and determines to admit to the circle of her friendship the more brilliantly colored male. Moths are so irresistibly attracted to a light as to fly into it without apparent power to withstand its influence. They repeat the flight again and again until they are destroyed. If they react so vigorously to the stimulus of the light, it seems not impossible that they may also act vigorously to the stimulus of color pattern, and that the male most beautifully colored, according to the nervous ideal of the female, should win her unconscious regard. At least it is certain that, in very many of the butterflies and moths, the attractive coloration is chiefly displayed when they are moving actively about; and when they alight and their enemies can the more easily capture them, they conceal their brilliant colorings. Most butterflies are very brilliant on the upper surface of the wings and very much duller on the under surface. Hence in flight they show their colorings exquisitely, but when they alight, and are thus more likely to be captured, they fold the brilliant surfaces together in an upright position. In this way not only is the dull side of the wings placed outward, but the wings themselves are placed edgewise to the sky, and it is from this direction that their enemies, the birds, are most likely to see them. Once upon the wing these creatures display their beauty with much greater safety because they can escape the birds very readily by use of their exceedingly jerky flight. The butterfly's motion is as irregular as any we have except the bat's. This eccentricity is one great element in their safety, and makes it less dangerous for them to display their attractive colorations.

One very large group of the night-flying moths have been named the "underwings," because of the fact that their hind wings are very much more brilliant than the front, and in lighting they fold the dull pair back over the bright, completely concealing them. These creatures are in the habit of resting in the daytime against walls, or stones, or the bark of trees. The similarity in color between their front wings, which alone show while sitting, and the background on which they rest, is most remarkable. One may pass them again and again, although they are of considerable size, and not notice them at all. Once let them display their hind wings and the brilliancy of their color always attracts immediate attention.

It is among birds, however, that brilliant coloration serves its most effective purpose. The birds are alert, exceedingly quick of sight, and are much more discriminating than insects in almost every respect. It is not so impossible that these creatures might even voluntarily prefer a distinctly more brilliant mate, though the voluntary character of the process is not essential to its success. Men certainly are constantly attracted to women for whose charm it would puzzle them to account. If this is true with regard to men, it is certainly probable that birds would be largely influenced by phases of attractiveness, of which they were observant, but unconscious.

Certain it is that in many birds the males are far more beautiful than the females. Perhaps the commonest illustration, and, at the same time, one of the best is found in the so-called red-wing or swamp blackbird. The male of this creature is a brilliant black, excepting that upon the angle of the wing, spoken of roughly as his shoulder, though in reality it is equivalent to our wrist, there appears a splendid orange patch with a border of lemon yellow. When he folds his wing he pushes this colored angle of the wing so deftly under the feathers of his shoulder as almost to conceal it. When in flight the bird is exceedingly conspicuous, showing, with every bend and twist of his body, his gorgeous epaulets. Meanwhile, the female is likely to pass unnoticed. She is dull in color and streaked like the grass among which she lives. During the mating season the male hovers about her, swaying from side to side in such a way as certainly to make it appear as if he realized his good points and was bringing them to bear as effectively as he knew how. After his mate has nested and is rearing her young, it would appear that the male uses his brilliancy to lure the observing enemy away from the nest containing his wife and children.

Another illustration of the remarkable superiority of the male over the female, in many parts of the bird world, is seen in the case of the common barnyard fowl. The rooster is so much more gorgeous than the hen that anyone reasonably acquainted with these birds cannot have failed to notice the fact. In some of our modern varieties we have by breeding colored them nearly alike. The original chicken is colored much like the common Leghorns. Shades of red and yellow decorate his neck and back, while the flight feathers of his wings and of his tail and the sickle feathers which ornament the rear of his back and hang over his tail are lustrous dark green. The hen meanwhile is very much less brilliant in her contrasts. I shall speak more fully of this in discussing polygamy.

The attraction of beauty is not the only lure by which a creature may win its mate. Sound may captivate as effectively as beauty. This is true of insects as well as of birds. Certain insects at least advise their mates of their presence by means of a sound which they emit. This is particularly noticeable among the group of straight-winged insects to which the grasshopper, katydid and cricket belong. The grasshopper has a ridge on the angle of his wing and a roughness on the side of his leg. When these two are rubbed together the result is sometimes a fiddling, sometimes a snapping or cracking sound, differing in different grasshoppers. I doubt not these sounds are pleasing to the female of the species, for they are always made by the male. The katydid, instead of fiddling in this way, has a sort of drum on the angle of his one wing, which he can rub over a tooth in the corresponding angle of his other wing, thus producing the familiar "katydid" sound. I have never succeeded in making a dead grasshopper fiddle, but I have long known how to make a dead katydid say "ka." Quite recently I have added to my accomplishment in this respect and can make it say "katy." The "did" part of the song still lies beyond my power. The crickets produce their sharp notes in much the same fashion as the katydids.

One observer of the chirping of the cricket says that the pitch of the song varies with the temperature. He has even worked out a formula by which one can tell the pitch of the chirp, if he knows the temperature, or, knowing the temperature, can determine the pitch. Of course this is too mechanical; yet it indicates that there must be considerable relation between the two; the warmer the cricket the happier he is.

It is the males among insects that chirp their love songs. The females never answer them. There is a peculiar notion that the female katydid, when thus accused of some offense, replies "katy didn't." The truth of the matter is that no female katydid ever replied to the accusations of her lover, if accusation it be. She is absolutely dumb, not having the drum upon her wings with which to reply. She is provided with ears wherewith to hear, and, strange to say, she keeps them on her elbow, as does also the cricket, while the grasshopper has his ears upon the side of his body.

Everyone who lives in the country, or goes into the country in the summertime, is sure to know the humming of the so-called locust. It is an unfortunate fact that the word locust may have several meanings. It is properly applied to one group of the grasshoppers. The creature most commonly called a locust is a cicada, or harvest fly. When the weather gets quite warm the cicada starts his love song. He has two long flaps to his vest, and under each flap he has a vibrating drum head. This is set shivering by a muscle on its under side. The female cicada again is silent.

It is among birds that the love song reaches its finest development. It may consist simply of a little chirp as in the chippy. It may consist of two notes of a different pitch repeated steadily, as in the tufted titmouse. It may attain considerable variation, as in the robin. But in the choir of our best singers, like the catbird, thrasher, and mocking bird, there is unending variation of notes. It seems almost impossible to doubt the charming quality of this voice upon the mate. It certainly is chiefly confined to the mating season, and is indulged in almost entirely by the males. This does not mean that a male does not sing excepting when he wishes to charm his mate. But the time when he is in his most exquisite feather and most charming mood is the time when he sings most sweetly, and this is the time when he is taking to himself a mate. The love joy may so overcrowd his life that he sings much and often, but the increase in its amount and character during the mating season seems to proclaim its purpose beyond a doubt.

In addition to the allurements above described there are certain peculiar behaviors of the animal during the mating season which are intensely interesting. Sometimes they consist simply of a wild delirium of joy, which overpowers the animal completely and makes him do wonderful things. Birds will fly with impetuous leaps in the air, mount higher and higher, singing wildly, only to turn suddenly at the top of the flight and drop promptly to the ground. I have seen such ecstatic flights in the oven bird and in our rollicking gold finch. I have seen a catbird on his way to a tree turn three somersaults, much like those performed by a tumbler pigeon, after which he alighted upon the bough. None of these acts seemed deliberately performed in front of the females, but I have seen three or four killdeer parading in most stately and precise manner, spreading their wings and fluffing their feathers, performing a sublimated cup-and-cake walk amid a circle of attracted females.

Even our little English sparrow, as I have previously mentioned, fluffs himself up and spreads his wings and prances around in front of his presumably adoring ladylove. But the weirdest performance of this sort I have ever seen is that shown by the male ostrich. When he becomes excited, swaying his body from side to side, he sinks slowly upon his knees, until his body touches the ground, his wings spread on either side and the feathers fluffed up so as to show every exquisite plume in all its splendid beauty. The long neck is laid back until the head, which is doubled sharply forward, is pressed almost against the back, and in this strange position he sways from side to side, apparently utterly oblivious, for a time, of everything. After about a minute of this performance, he seems slowly to come to himself and rise again to his feet. Now he is particularly likely to make vicious attack upon anything within reach.

It is not only necessary that the animal should be able to attract a mate. There may be more than one claimant for the damsel's affection. In many animals we see provisions whereby the male may effectively deal with his rivals. This is especially likely to be the case if the animal be a polygamist. In every species there are produced about as many males as females. If the polygamous habit leads one male to gather about him a group of females, with whom he mates, it is evident that he is displacing an equal number of rivals, and they are not willingly displaced. Accordingly we find that polygamy is usually accompanied by a belligerent disposition on the part of the males. In our ordinary barnyard fowl this trait is very evident. The rooster not only domineers over the hens, not only struts about among them in stately fashion and gives vent to his feelings by his sonorous voice, he must also drive away from the neighborhood any rivals for the affections of his wives. Hence the rooster attacks upon sight the neighboring rooster, and battles with him to his entire discomfiture and sometimes to the death.

Among the members of the deer family this particular phase of the relation between the sexes has produced in the males, and only very rarely in the females, the magnificent branching horns. These are intended not so much as a protection against the enemy as for an offensive weapon in the battle for the mates.

Beautiful and stately as are these magnificent horns, they last only for a part of the year. We begin to understand their meaning. When the wolf is hungriest, toward the close of the bitter winter, the deer is without horns. When the time for mating comes, the deer within a few weeks grows his horns, which at first are covered with a plushlike coating, known as velvet. After a while this dries and he rubs his horns against the trees until they are clean and smooth. Now he is ready for the battle royal.

In the case of the fur seals polygamy has carried its specialization of the males to a remarkable extent. The bull seals are several times as large as the cows, and are provided with terrific canine teeth. With these they battle with a violence that very often results in the death of one of the combatants. A successful bull seal who has gathered about him a cluster of seal cows is seamed and scarred with the marks of his annual combats.

One more type of adaptation can be profitably considered. Animals have developed many devices which serve for the protection of their young. The wonderful silk spun by the spider was evidently primarily intended to serve as a covering for the eggs. Probably all of our spiders agree in using the silk for this purpose. Many of them employ it for practically no other, though there are half a dozen different uses to which different spiders may put their silk. Under these conditions we have a right to infer that silk was primarily developed as a coating for the eggs. In the case of some of our spiders a little fluffy mass of silk covers the egg, while a firmly woven sheet of silk covers both egg mass and fluff, holding it flat against a wall or the trunk of a tree. In some of the higher spiders, notably our bank spiders, the silken covering becomes an effective cocoon, spherical in shape, with a little opening at the top like the neck of a small bottle. The egg cocoon is woven in a mass of tangled silk between the branches of some tough weed which will be sure to outlast the winter. Into the egg cocoon the spider may place one thousand or more eggs. Having thus provided her children with a snug winter home, the spider dies. When spring comes with the warm rays of the sun, the eggs hatch and the cocoon becomes a creeping mass of minute spiders. At the time these spiders appear there is nothing for them to eat. The obvious way out of this difficulty is taken. At once there begins a progressive party. Spider fights with spider, and the prize in each conflict is the body of the victim, which is promptly eaten. The winners in the first round pair off again, and a little later, as hunger drives them, another set of combats comes on, resulting in another halving of the number of spiders in the cocoon. This process continues until not more than one-tenth of the original number of spiders remains. By this time they have gained sufficient strength of leg and jaw, and sufficient dexterity in the use of both, to make it safe for them to venture out and try their fortunes among the accidents of a strenuous world. There can be little doubt after this long process has worked its final results which tenth remains. Chance plays but small part in this game. It is the fittest that survive. When this procedure goes on generation after generation, the result must necessarily be that the spiders grow fitter and fitter for their work. This method is hard on the little spider, but it makes good spiders.

Most insects die before their eggs hatch; accordingly they can pay no attention to their own children. Whatever arrangements are provided for the safety and strength of these offspring must be provided before they appear. About the only care the majority of insects take in this direction is to see that the eggs are placed where the young shall find food as soon as they emerge. Insects' eggs are very small, and as a consequence the creatures which emerge from them are likewise exceedingly minute. As a result they cannot be expected to hunt far for their food. Different insects use different devices by which to overcome this difficulty. The katydid, for instance, must die with the approach of fall. Her children will not appear until the following year. Her food consists of leaves, but to lay the eggs in such a situation would be a fatal process, because the leaf will drop off before the eggs hatch. Accordingly, the katydid lays its shield-shaped eggs in a double row near the end of a young twig. Next year when the weather is sufficiently warm to hatch katydids, it is also warm enough to force the buds on the end of the twigs. When the katydids arrive their jaws are young and tender, but so are the leaves upon which they are born. Hence there is little difficulty on the part of the young katydids in finding an abundance of food. By the time the leaves have grown tougher, the katydid's jaws are stronger, and the leaves will still serve as food.

Everyone who is at all familiar with country life and gardening is familiar with what is called the potato or tomato worm. It is a long, green, smooth, caterpillar, as long and as fat as your finger and provided with a horn upon his tail. The gardener may not know that after a while this creature will burrow into the ground, and there change into an oblong brown mass with a sort of a pitcher handle at one side. Next year this pupa will split down the back, and from out of the brown case will come a hawk-moth, which soon will fly with rapidly quivering wings and feast upon the nectar of our moon flowers or on that of the "Jimson" weed. Those who have cleaned these pests from the potato or tomato vines will often have noticed one of them covered with what look almost like grains of rice. This appearance reveals an interesting story. Some time earlier an insect that looked very much like a dainty wasp with a rather long sting in its tail hovered over the caterpillar. This is the ichneumon fly. Eventually lighting upon the caterpillar's back, it punctured the skin with its sting, and deposited eggs within the caterpillar's body. These eggs soon hatched and the little grubs worked their way through the body of its host. The infested victim feeds upon leaves and fills itself with rich food. These parasites eat the food, and, try as it may, the caterpillar does not succeed in getting fat. After the grubs have gotten their full growth, each of them eats its way through a little hole to the outside of the caterpillar's body. Here it spins around itself a little white case, and looks like a rice grain. As the caterpillar moves about, these seeming rice grains are rubbed off and fall to the ground. Next year there will come up new ichneumon flies to sting fresh caterpillars and repeat the entire process.

Another remarkable provision for the young on the part of insects is seen in the behavior of the big sphex wasp, known as the cicada killer. The cicada, it will be remembered, is what is commonly called a locust. The cicada killer is a magnificent big wasp, whose body is nearly an inch long, banded with black and yellow, while the wings are colored a smoky brown. This muscular wasp digs a long tunnel eight or ten inches deep, which ends in a slightly larger room. Having provided the location, he now sallies forth in search of the cicada. The heavy song of the male probably serves as a guide to the wasp in case of scarcity of cicadas, but the killer has apparently little difficulty in finding his prey. The wasp pounces upon the insect, and in spite of its strength and the thrashing of its vigorous wings punctures it with his sting again and again. The poison of the sting entering into the nerve centers gradually paralyzes, but usually does not kill, the cicada. Now the killer carries its prey home, pushes it to the bottom of the tunnel and deposits upon it a single egg. The wasp closes up the hole and leaves the place. When the egg hatches and the grub of the wasp emerges, it finds a big cicada just at hand, upon which it feeds. By the time the cicada is completely devoured, the wasp grub has obtained its full growth. After a short period of development a new sphex wasp is ready to work its way out of the tunnel, find a mate, dig a hole, and safely provide for its own children.

Still more remarkable adaptations for the care of the young appear among the birds. Here the eggs are not to be deserted, but are to be cared for until the young appear. These again must have attention until such time as they are quite able to take care of themselves. The birds are warm-blooded animals, and even their young, while they are developing in the egg, are warm-blooded. Consequently the temperature of the egg must be maintained evenly and uniformly, or there will be no development.The fish may drop its eggs carelessly upon the bottom of the stream. A frog may deposit them in a mass of jelly and leave them forever. A turtle may bury its eggs in a sand bank and abandon them to their fate. The warm blood of the young bird demands more attention than this. Accordingly, the parent bird has learned to make for itself some sort of nest, in which the young may be kept properly warm until they are developed. The ancestral bird, who was to be the progenitor of the entire bird class, must have had some very simple method of providing a place in which its eggs might be hatched. As the descendants of this original bird have passed into new situations, the various lines have taken upon themselves different shapes until we have the multiform birds of to-day. The habits of the birds have also varied. Each has adapted itself to the situation in which it found itself, and no adaptation has been more varied and effective than the adjustment of the nesting site. Nests are found upon the ground, in the bushes, on the lower limbs, in the crotches of the trees, in the trunks of the trees, upon their very summits, and on the tops of inaccessible crags. To every sort of situation some bird has been enabled to adapt itself. This has made it possible for very many more birds to thrive than could have found a place in the world, had they all lived upon the same plan.In the case of the bank swallow his nest may be a very simple contrivance, consisting only of a tunnel running back into a bank, and widening at the back. Some material that will soften the bed upon which eggs are to be laid must be placed in this cavity. The whole home is a very simple and crude affair. But little better is the arrangement which the woodpecker calls a home. This has been cut into the dry wood of a defective tree. No woodpecker can make his home in absolutely solid sapwood. Hence the first labor of the woodpecker must consist in finding a place in which it can dig. If there is an old stump of a limb sticking up, the problem is readily solved. Such wood has no sap in it, and is brittle enough to be easily dug out. But, if there be no such stub, the woodpecker will find a suitable place in most trees. At some time or other almost every tree loses a big limb. When such accident occurs there will always be in the old trunk a region through which sap once went to this limb. This region, deprived of its function, goes completely dry, like the heartwood of the tree, and it is into such material as this that the woodpecker succeeds in drilling his well-protected home.

As birds rise higher in the scale the nest-building becomes a more complicated affair, and after a while we find a well-woven substantial nest, through which even the air will not chill the eggs enough to prevent their hatching, while the warmth is supplied by the mother's body. It is often a matter of surprise to many people that a bird should contrive to build a nest so exquisitely circular. The trick, after all, is not quite so difficult as it looks. The robin gathers up a few sticks and places them as the beginning of the platform. More and more are brought and woven into each other, making a framework altogether too big for the nest. Then mud is brought and plastered inside of this. With the plastering of this mud the careful circularity of the work begins. Every time a little material has been added the robin sits down in the nest and revolves her body, in this way shaping the interior much as the potter shapes a pot. In the case of the artisan, it is the pot that revolves. In the case of the robin, the bird itself revolves. The effect is the same in both cases—a circular vessel is produced. A little lining added to the interior of the nest softens it for the reception of the eggs. In this exquisite home the robin lays her eggs, and sits upon them until they are developed enough to hatch, and then feeds the young until they are old enough to feed themselves.

Far more remarkable than any of the devices thus far described are the wonderful developments which have come in the class of animals known as the mammals. Here the most wonderful protection is made for the care and feeding of the young. But this is to be the subject of a separate chapter.

As long as we thought of each sort of animal as being a separate species shaped in the beginning by the hands of the Creator, each of these devices seemed to us a new manifestation of the Divine Providence, whose fertile planning had conceived so many methods of providing for his children. Unconsciously we thought of God acting as man acted. Each animal seemed a purely separate invention purposely designed for an especial place. Now we understand the plan in creation better, and see that each animal has come from another not quite like itself, some distance back, and this from still another. Our admiration for these devices as they arise through evolution is no less, but takes on another form.