The doctrine of evolution, according to Herbert Spencer, further considered.

In the last two preceding chapters I have examined what Mr. Spencer regards as the direct supports of the doctrine of evolution. I have now to consider the different orders of facts which, as he claims, yield to it indirect support. These are the facts derived from classification, from embryology, from morphology, and from distribution. An explanation is here needful of the sense in which he uses these respective terms, before the reader, who is not accustomed to them, is called upon to understand and appreciate the argument:

1. By classification is meant an arrangement of organic beings in some systematic manner, according to attributes which they have in common, and which may form the principle of a division into different classes or families. Pointing out that in the early history of botanical and zoÖlogical science the tendency was to make classifications according to a single characteristic, Mr. Spencer reminds us that later naturalists, by attending to a greater number of characteristics, and finally to the greatest number that can be found to be common to various classes of vegetable and animal organisms, have constructed systems of classification which, in place of a linear or a serial order, have exhibited the alliances of different groups, then the sub-groups, and the sub-sub-groups, so that the divergences and redivergences become developed, while the resemblances which obtain are preserved throughout the whole class. But it is at once apparent that, although classification, on whatever principle it is conducted, may be valuable as a means of fixing in the mind the resemblances or differences of structure that obtain in the different orders of organized beings, as, for example, among the vertebrate or the invertebrate animals, the flowering or the flowerless plants, the seeds naked or the seeds inclosed in seed-vessels, yet that any other system of classification, based upon other resemblances or differences which actually present means of grouping or separating the different families of organized beings, is just as valuable an aid in the investigation of facts. How far any classification affords an argument, or the means of constructing an argument, which will yield a support to the doctrine of evolution superior to that which it yields to the doctrine of special creations, is of course a question.

2. Embryology: This is the term employed to express that branch of inquiry which is concerned in a comparison of the increase of different organisms through the stages of their embryonic life, and in noting at different stages of this growth the characters which they have in common with each other; the resemblances of structure which at corresponding phases of a later embryonic stage are displayed by a less extensive multitude of organisms; and so on step by step, until we find the class of resembling embryos becoming narrower and narrower, and then we finally end in the species of which a particular embryo is a member. This process of tracing and eliminating embryonic resemblances is said to have "a profound significance"; because, beginning with a great multitude of resemblances between the embryonic development of different organisms, it reveals the divergences which they take on, and through every successive step we find new divergences, by means of which "we may construct an embryological tree, expressing the developmental relations of the organisms, resembling the tree which symbolizes their classificatory relations." We thus arrive at "that subordination of classes, orders, genera and species, to which naturalists have been gradually led," and which is said to be "that subordination which results from the divergence and redivergence of embryos, as they all unfold."[79] On this mode of comparing the embryonic development of different organized beings Mr. Spencer builds a scientific parallelism, which indicates, as he claims, a "primordial kinship of all organisms," and a "progressive differentiation of them," which justifies a belief in an original stock from which they have all been derived. In what way this method of investigation destroys or tends to destroy the hypothesis of special creations, or how it affords an important support to the doctrine of evolution, will be considered hereafter.[80]

3. Morphology, or the science of form, involves a comparison of the structure of different organisms in their mature state; an ascertainment of the resemblances between their structures, and of the community of plan that exists between them. Here, as in the aids derived from classification and embryology, it is claimed that the fundamental likenesses of forms of structure have a meaning which is altogether inconsistent with the hypothesis of predetermined typical plans pursued throughout immensely varied forms of organisms.

4. Distribution: This is the term applied to the phenomena exhibited by the presence of different organisms in different localities of the globe; or, as Mr. Spencer phrases it, "the phenomena of distribution in space." These phenomena are very various. Sometimes, it is said, we find adjacent territories, with similar conditions, occupied by quite different faunas. In other regions, we find closely allied faunas in areas remote from each other in latitude, and contrasted in both soil and climate. The reasoning, as given by Mr. Darwin and adopted by Mr. Spencer, is this: that "as like organisms are not universally or even generally found in like habitats, nor very unlike organisms in very unlike habitats, there is no predetermined adaptation of the organisms to the habitats." "In other words," Mr. Spencer adds, "the facts of distribution in space do not conform to the hypothesis of design." The reason why they do not is claimed to be that there are impassable barriers between the similar areas which are peopled by dissimilar forms; whereas there are no such barriers between the dissimilar areas which are peopled by dissimilar forms. The conclusion is, "that each species of organism tends ever to expand its sphere of existence—to intrude on other areas, other modes of life, other media." That is to say, there is a constant competition among races of organisms for possession of the fields in which they can find the means of subsistence and expansion; and this leads to new modes of existence, new media of life, new structures and new habitats.

The reader can now retrace his steps, and advert to the facts that are relied upon, under the four heads of the argument:

1. With regard to the argument derived from classification: it is to be observed that any system of classification is in a certain sense artificial, and at all events is manifestly conventional. But, in order that no injustice may be done to this branch of the argument for evolution, I shall state it in its full force. The classifications which naturalists make of the different organized beings according to their resemblances and differences reveal the fact of unity amid multiformity. This fact it is said points to propinquity of descent, "which is the only known cause of the similarity of organic beings." It is the bond, hidden indeed by various degrees of modification, but nevertheless revealed to us by the classifications which display the resemblances. Again, we have, it is said, in the influence of various conditions of animated organisms, "the only known cause of divergence of structure." Classification reveals to us these divergences. We have, then, the bond of resemblances which indicate propinquity of descent, and the divergences of structure produced by varying conditions of life. Put the two together, and we have remarkable harmonies of likenesses obscured by unlikenesses; and to this state of facts it is claimed that no consistent interpretation can be given, without the hypothesis that the likenesses and the unlikenesses were produced by the evolution of organisms out of organisms by successive generation, through a great lapse of time.

This argument contains no inconsiderable amount of assumption. While it may be true that some naturalists do not assign any cause for the similarity which obtains among organic beings excepting their descent from a common ancestral stock, it is not true that the similarity of structure is inconsistent with the hypothesis of another cause, namely, the adoption of a general plan of structure for a large class of organisms, and an intentional variation in those parts of structure which mark the divisions of that class into species that are very unlike. It is true that evolutionists treat with scorn the idea of a pattern of structure followed throughout a class of animals, but made by designed adaptations to coalesce with differences that mark the peculiarities which distinguish one organism of that class from all the others. Mr. Spencer, for example, observes that "to say that the Creator followed a pattern throughout, merely for the purpose of maintaining the pattern, is to assign a motive which, if avowed by a human being, we should call whimsical."

Let us now follow this mode of disposing of the hypothesis of special creations, by adverting to some of the facts that are adduced in its summary condemnation; and, although the passage which I am about to quote is found in Mr. Spencer's work under the head of morphology, the illustration applies equally well to his argument from classification. Speaking of fundamental likenesses of structure, he says: "Under the immensely varied forms of insects, greatly elongated like the dragon-fly, or contracted in shape like the lady-bird, winged like the butterfly, or wingless like the flea, we find this character in common—there are primarily twenty segments. These segments may be distinctly marked, or they may be so fused as to make it difficult to find the divisions between them. This is not all. It has been shown that the same number of segments is possessed by all the Crustacea. The highly consolidated crab, and the squilla with its long, loosely-jointed divisions, are composed of the same number of somites. Though, in the higher crustaceans, some of these successive indurated rings, forming the exo-skeleton, are never more than partially marked off from each other, yet they are identifiable as homologous with segments, which, in other crustaceans, are definitely divided. What, now, can be the meaning of this community of structure among these hundreds of thousands of species filling the air, burrowing in the earth, swimming in the water, creeping about among the sea-weed, and having such enormous differences of size, outline, and substance, as that no community would be suspected between them? Why, under the down-covered body of the moth and under the hard wing-cases of the beetle, should there be discovered the same number of divisions as in the calcareous framework of the lobster? It can not be by chance that there exist just twenty segments in all these hundreds of thousands of species. There is no reason to think it was necessary, in the sense that no other number would have made a possible organism. And to say that it is the result of design—to say that the Creator followed this pattern throughout, merely for the purpose of maintaining the pattern—is to assign a motive which, if avowed by a human being, we should call whimsical. No rational interpretation of this, and hosts of like morphological truths, can be given except by the hypothesis of evolution; and from the hypothesis of evolution they are corollaries. If organic forms have arisen from common stocks by perpetual divergences and redivergences—if they have continued to inherit, more or less clearly, the characters of ancestral races, then there will naturally result these communities of fundamental structure among extensive assemblages of creatures, that have severally become modified in countless ways and degrees, in adaptation to their respective modes of life. To this let it be added that, while the belief in an intentional adhesion to a predetermined pattern throughout a whole group is totally negatived by the occurrence of occasional deviations from the pattern, such deviations are reconcilable with the belief in evolution. As pointed out in the last chapter, there is reason to think that remote ancestral traits will be obscured more or less according as the superposed modifications of structure have or have not been great or long maintained. Hence, though the occurrence of articulate animals, such as spiders and mites, having fewer than twenty segments, is fatal to the supposition that twenty segments was decided on for the three groups of superior Articulata, it is not incongruous with the supposition that some primitive races of articulate animals bequeathed to these three groups this common typical character—a character which has nevertheless, in many cases, become greatly obscured, and in some of the most aberrant orders of these classes quite lost."[81]

Whatever may be the explanation suggested by one or another hypothesis as to the mode in which this uniformity of structure came to exist, it is certain that it does exist. Twenty segments are found in hundreds of thousands of species which are immensely different from each other in size, outline, substance and modes of existence. Here, then, is a plan. There is a pattern, on which all these different organisms are constructed with a common peculiarity. It is averred that this could not have been the result of design, because this would be to impute to the Creator a whimsical motive, namely, that he followed the pattern throughout a vast group of different organisms merely for the purpose of following it. On the contrary, it may be contended that this uniformity of plan, this repeated pattern, affords the highest probable evidence of design; and that the supposed whimsicality of motive will entirely disappear as soon as we reach a purpose which may have had very solid reasons for this uniformity of structure. When we reason about the works of the Creator, we are reasoning about the methods of a being who, we must suppose, is governed by a purpose in all that he does. In reasoning about the methods of such a being, it is entirely unphilosophical to suppose that he has done anything merely for the sake of doing it, or for the sake of exercising or displaying his powers in repetitions that had no practical value. In order to reason consistently with the supposed attributes of the Creator, we should endeavor to find the value of any given pattern which we discover in a certain very large class of organisms differing widely from each other in other respects; and in order to find that value it is by no means essential to make out that the particular plan of construction was necessary to the making of any organism whatever. The true question is, not whether twenty segments were necessary to the construction of any organism, but whether, in each of the different species, this peculiar number of divisions was useful to each particular organism. If naturalists of the evolution school, instead of looking at everything through the medium of a certain theory, would in their dissection, for example, of the framework of the lobster, the body of the moth, and the body of the beetle, furnish us with facts which would show that these twenty divisions are of no use either for strength, or resistance, or suppleness, or adaptation to what is contained within them, we should have a body of evidence that could be claimed as tending to overthrow the hypothesis of intentional design. They might then speak of the repetition of this pattern as whimsical, upon the hypothesis that it was a repetition by design. But so little is done by this class of naturalists to give due consideration to the value of such repetitions, and so little heed is paid to the truth that the Creator does nothing that is useless—a truth which all sound philosophy must assume, because it is a necessary corollary from the attributes of the Creator—that we are left without the aid which we might expect from these specialists in natural science. Is it, then, impossible to discover, or even to suggest, that for each of these organisms this number of twenty divisions had a value? If they were of no value, we may safely conclude that they would never have existed, unless we ignore the hypothesis of infinite wisdom and skill. That hypothesis is a postulate without which we can not reason on the case at all. With it, we have as a starting-point the conception of a being of infinite perfections, who does nothing idly, nothing from whim, nothing from caprice, and nothing that is without value to the creature in which it is found. So that, while we can not in all cases as yet assign that value, we have the strongest reasons for believing that there is a value; and, instead of asserting that an extensive community of structure throughout a great branch of the animal kingdom has no meaning excepting upon the doctrine of evolution, it is the part of true science to assume that it may have another meaning, and to discover if possible what that other meaning is. This is the part of true science, because it is the part of sound philosophy. There is another remark to be made upon Mr. Spencer's reasoning on this particular case of a community of pattern. He says that it can not be imputed to chance. It was, then, either an intentional design, or it came about through the process of descent "from common stocks, which process was at the same time producing perpetual divergences and redivergences." Without turning aside for the present to ask from how many common stocks, it may be shown as in the highest degree probable that the occasional deviations from the pattern did not arise by the evolution process, because that process has in itself an element of chance which is fatal to the theory. The assertion is that "an intentional adhesion to a predetermined plan throughout a whole group is totally negatived by the occurrence of occasional deviations from the pattern." Let this assertion be examined first in the light of facts, and secondly by the absence of facts.

The hypothesis is that some primitive race of articulated animals, possessed by some means of the twenty segments, transmitted this ancestral trait to hundreds of thousands of species having no community of structure in other respects. Unfortunately for the theory, no figures can measure the chances against the preservation of a single pattern through such a multitude of differing organisms descending from a common stock. Infinity alone can express the chances against such a result. While, according to the theory, the deviations from the original type were constantly working out new organisms of the most diversified forms, until there came to be hundreds of thousands of new species differing from each other in all but this one peculiarity—a diversity which is supposed to have been caused by the fundamental law of evolution—how did it happen that the same law did not break this uniformity of articulation? If it was potent enough to differentiate the enormous multitude of these animals in all other traits, why did it not vary the number of segments with which the primitive race was endowed? Is the law of evolution limited or unlimited? If it is limited in its effects, then there are patterns of animal structure which it has not modified, and the presence of which in hundreds of thousands of different species must be explained as a form of structure designed for some end that was to be common to a great multitude of different beings. If the law of evolution was unlimited in its power, then the community of pattern has had to undergo chances of destruction or discontinuance that are immeasurable; as there can be no measure which will represent to the mind the infinitely diversified and innumerable causes that have produced the dissimilarities which compel a classification into the different species, upon the hypothesis of their descent from a common stock. Grant, too, for the purpose of the argument, that the occasional deviations from the pattern of twenty segments, producing a few groups with a smaller number of articulations, are reconcilable with the belief that some later ancestral form became endowed with the smaller number which it transmitted to its descendants. How came that later ancestral form to be endowed with the smaller number of segments? Was there a still more remote ancestral race, which in some way became possessed of the smaller number, or did the spiders and the mites, in the countless generations of evolution, branch off from ancestral races having the full number of twenty segments? Upon either supposition, what an infinity of chances there were, against the natural selection of the smaller number, and against its preservation as the unvarying type of articulation found in the spiders and the mites! The supposition that the number of twenty segments was decided on for the three groups of superior Articulata for the mere sake of adhering to a pattern is doubtless unphilosophical. But it is not unphilosophical to suppose that whatever amount of articulation is found in each species was given to it because in that species it would be useful. If in some of the most aberrant orders of these animals the articulation is greatly obscured, or not found at all, the conclusion that it was not needed, or not needed in a like degree, is far more rational than the theory which commits the particular result to an infinity of chances against it; or which supposes it to have been worked by a process that might have produced a very different result, since it can not be claimed that natural selection works by methods of which any definite result can be predicated more than another.

Thus far I have considered Mr. Spencer's argument from the Articulata in the light of the facts that he adduces. Let us now test it by the absence of facts. In a former discussion, I have asked for facts which show, aside from the theory, that any one species of animal, distinctly marked as a continuing type, is connected by intermediate types or forms with any pre-existing race of another character. Take this class of the articulated animals, said to be of hundreds of thousands of different species having no community of form but this of articulation, and now known as perfect organisms, each after its kind. What naturalist has discovered the continuity of lives with lives, which would furnish the steps of descent of any one of this species from an antecedent and a different species? It is very easy to construct a theory, and from it to argue that there must have been intermediate links, which, if discovered, would show the continuity of lives from lives which the descent of one organism from another necessarily implies. To a certain extent, within certain limits, the sub-groups and the sub-sub-groups of the articulated class of animals, which classification or morphology reveals, may lay the foundation for a theoretical belief in an ancestral stock from which the different and now perfect forms of these distinct animals may have become developed by successive changes of structure. But the extent to which connected changes can be actually traced in the animal kingdom is extremely limited; and the important practical question is whether any one fact, or class of facts, has been discovered which will warrant the belief that beings of totally dissimilar forms and habits of life have, without any design, been evolved by the ordinary process of successive generation, through the operation of causes that have gradually modified the structure in all respects save one, and have at the same time enabled or allowed that one peculiarity of structure to escape from the influences which have modified both structure and modes of life in every other respect. Why, for example, upon the hypothesis of descent from a common stock, has that stock deviated under the influences of natural selection into the lobster, the moth, and the beetle, and yet the community of twenty segments of articulation has entirely escaped the effect of those influences? No reason can be assigned for the fact that it has escaped those influences, excepting that it was originally designed, and was impressed upon the proto-typical stock with such force as to place it beyond the reach of all such causes of modification as those which are ascribed to natural or sexual selection. Without the latter supposition, those causes were just as potent to bring about a modification in the number of articulations as they were to bring about all the astonishing diversities of structure and modes of life that we see, and therefore the most probable conclusion from the fact of this uniformity of the twenty segments is, that there was a barrier placed in this whole class of organisms, which has limited the modifying force of the supposed process of evolution, for the reason of some peculiar utility in this plan of articulation.

Perhaps it will be said that the process of evolution itself tends to the preservation of whatever is most useful, while the modifications are going on which develop new organs and new structures; and that thus, in the case before us, the twenty segments have been preserved throughout an enormous group by one of the fundamental laws of evolution, so that, if there is any peculiar utility in the twenty segments, that utility has been answered by the very process of gradual descent of one organism from another. But the difficulty with this reasoning is, that while it assumes for the modifying influences of natural and sexual selection a range of fortuitous causes sufficient to change the ancestral type into the acquisition of vastly diversified organs, powers, and modes of existence, so as to constitute new animals, it yet assumes that, by some recognition of a superior and paramount utility in the particular number of segments, the law of evolution has preserved that number from the influence of causes which have changed everything else. Now, the range of causes which was sufficiently varied, accidental, long-continued and complex to produce the diversities of structure in all other respects, by the infinitely modifying influences which have developed new organs and new modes of existence, must also have been of a sufficiently varied, accidental, long-continued, and complex character to have broken this plan of the twenty segments, unless we suppose that in some mysterious and inexplicable manner the different generations of these beings were endowed with some kind of sagacity which would enable them to strive for the preservation of this one peculiarity, or unless we suppose that Nature was ever on the watch to guard them from its destruction or variation, on account of its peculiar utility. The first supposition is not in accordance with the evolution theory; for that theory rejects all idea of conscious exertion on the part of any of the organisms. The second supposition leads us at once to the inquiry, how came it to be imposed upon a whole group of beings as a law of nature, that whatever utility of structure was of paramount importance to the whole group should be preserved against the modifying influences that were to produce species differing absolutely from each other, through hundreds of thousands of varieties, in every other feature of their existence? Can we get along here without the hypothesis of design? And, if there was such design, how does the fact of this uniformity amid such diversity become an argument against the hypothesis of a Creator? Or, how does it tend to displace the hypothesis of special creations, when we find that the very process of so-called evolution has failed to break the uniformity of a pattern that is conceded not to have been the result of chance, although that pattern was exposed to just as many and as powerful causes of modification as those which are assumed to have brought about the modifications in every other feature of the animal existence? The truth would seem to be, that the uniformity amid so great a diversity was either the result of a design which placed it out of the reach of all the modifying influences, or else it has, by a most incalculable result, escaped from the effect of those influences by a chance in which the ratio of one to infinity can alone measure the probability of such an escape.

Let us now advert to another of Mr. Spencer's illustrations of the futility of the "supernatural" and of the rationality of the "natural" interpretation.[82] This illustration is derived from what are called "homologous" organs; and the particular instance selected is the vertebral column.[83] There are creatures, such as snakes, a low order of the vertebrate kingdom, in which the bony axis is divided into segments of about the same dimensions from end to end, for the obvious advantage of flexibility throughout the whole length of the animal. But in most of the higher vertebrata, some parts of this axis are flexible and others are inflexible; and this is especially the case in that part of the vertebral column called the sacrum, which is the fulcrum that has to bear the greatest strain to which the skeleton is exposed, and which is yet made not of one long segment or vertebra, but of several segments "fused together." Mr. Spencer says: "In man there are five of these confluent sacral vertebrÆ; and in the ostrich tribe they number from seventeen to twenty. Why is this? Why, if the skeleton of each species was separately contrived, was this bony mass made by soldering together a number of vertebrÆ like those forming the rest of the column, instead of being made out of one single piece? And why, if typical uniformity was to be maintained, does the number of sacral vertebrÆ vary within the same order of birds? Why, too, should the development of the sacrum be the roundabout process of first forming its separate constituent vertebrÆ, and then destroying their separativeness? In the embryo of a mammal or bird, the substance of the vertebral column is, at the outset, continuous. The segments that are to become vertebrÆ, arise gradually in the midst of this originally homogeneous axis. Equally in those parts of the spine which are to remain flexible, and in those which are to grow rigid, these segments are formed, and that part of the spine which is to compose the sacrum, having passed out of its original unity into disunity by separating itself into segments, passes again into unity by the coalescence of these segments. To what end is this construction and reconstruction? If, originally, the spine in vertebrate animals consisted from head to tail of separate movable segments, as it does still in fishes and some reptiles—if, in the evolution of the higher vertebrata, certain of these movable segments were rendered less movable with respect to each other, by the mechanical conditions to which they were exposed, and at length became relatively immovable—it is comprehensible why the sacrum formed out of them should continue ever after to show more or less clearly its originally segmented structure. But on any other hypothesis this segmented structure is inexplicable."

We here see the predominating force of a theory which refuses all possible rationality to any hypothesis but its own. The confident tone with which facts are arrayed and are then pronounced inexplicable upon any other hypothesis than that which the writer asserts, without one scintilla of proof of their tendency to exclude every other supposition, renders the refutation of such reasoning a wearisome task. But there is here one plain and sufficient answer to the whole of the supposed difficulty. The evolution theory, in this particular application of it, is that originally there were vertebrate animals in which the spine consisted of separate movable segments from head to tail, as it does now in fishes and reptiles; but, as the higher vertebrata were evolved out of these lower forms, the movable segments were rendered less movable with respect to each other, and at length in the sacrum the segments became relatively immovable, and yet the originally segmented structure was retained in this part of the column, by force of the propinquity of descent from an antecedent type which had the whole column divided into movable segments. Upon no other hypothesis, it is asserted, is this result explicable.

Mr. Spencer's analysis of the sacrum is somewhat defective. It is, as he says, that part of the vertebrate column which in the higher class of vertebrate animals is, during foetal life, composed, like all the rest of the column, of distinct vertebrÆ. These vertebrÆ, like the others, are flexible in the foetal stage, but after birth they become coalesced or united into one piece, instead of remaining in separate pieces. Thus far, Mr. Spencer's description is, I am informed by anatomists, correct. But the questions which he propounds as if they were unanswerable upon the assumption that this change is inexplicable upon any other hypothesis than that of the evolution of the higher vertebrata out of the lower vertebrate animals, and that the sacrum, with its continuous piece, has retained the segmented outward form by force of the descent, demand closer consideration. Let us trace the process of formation in the human species, and then see what is the just conclusion to be derived from it. In the embryonic condition, the substance which is to form the vertebral column is continuous. As the foetus is developed, this substance separates itself into the segments which are called vertebrÆ, and these segments remain flexible and movable throughout the column. After birth, the five lower segments become united in what is substantially one piece, but of course the marks of the original segments remain. This is what occurs in the origin and growth of the individual. Now, looking back to the period when this species of animal did not exist, and supposing it to have been specially created in the two related forms of male and female, endowed with the same process of procreation and gestation that has been going on ever since there is any recorded or traditionary knowledge of the race, why should not this very growth of the sacrum have been designed, in order to produce, after the birth of the individual, that relative rigidity which would in this part of the vertebral column be useful to an animal destined to an upright posture of the whole skeleton and to the habits and life of a biped? And, if we extend the inquiry to other species, why should we not expect to find, as in the case of an oviparous vertebrate like the ostrich, a repetition of the same general plan of forming the spinal column, for the same ultimate purpose, with such a variation in the number of original segments that are to constitute the sacrum as would be most useful to that bird, thus establishing for the ostrich a sacrum that in a reptile or a fish would not only not be required, but would be a positive incumbrance? Upon the hypothesis of special creations of the different species of vertebrate animals, every one of Mr. Spencer's questions, asked as if they were unanswerable, can receive a satisfactory solution. Thus, he asks, "Why, if the skeleton of each species was separately contrived, was this bony mass [the sacrum] made by soldering together a number of vertebrÆ like those forming the rest of the column, instead of being made [aboriginally] in one single piece?" The answer is, that in the establishment of the process of gestation and foetal growth, if a human artificer and designer could have devised the process, he would have selected the very one that now exists, for certain obvious reasons. First, he would have designedly made the process to consist, in the embryo, of a division of the substance which was to form the vertebral column in a continuous and uniform division into segments, because the whole column is to have at first the flexibility that may be derived from such a division. Secondly, when the time was to arrive at which the formation of the sacrum, with its practical continuity of a single piece, was to commence, he would select the number of the lower vertebrÆ that would make a sacrum most useful to the particular species of animal, and would weld them together so as to give them the relative rigidity and action of a single piece. But as the whole formation is the result of a growth of the sacrum out of a part of the slowly forming column originally divided into vertebrÆ, the marks of these separate vertebrÆ would remain distinguishable, while they would cease to have the mechanical action of separate vertebrÆ.

Another of Mr. Spencer's questions is, "Why, if typical uniformity was to be maintained, does the number of sacral vertebrÆ vary within the same order of birds?" The answer is the same as that which assigns a reason for all other variations in the skeleton of animals of the same order but of different varieties, namely, the special utility of the variations in the number of sacral vertebrÆ that would be most useful in that variety. The typical uniformity maintained is a uniformity in the process of growth and formation, down to a point where the variations are to come in which mark one animal from another; and I have more than once had occasion to suggest that the typical uniformity, and its adaptation to the varying requirements of different beings, is the highest kind of moral evidence of the existence, wisdom, and power of a supreme artificer, and that it militates so strongly against the doctrine of evolution that, without more proof than can possibly be claimed for that doctrine, we ought not to yield to it our belief.

The theory that the original condition of all vertebrate animals was that of separate movable segments throughout the spinal column, as it is now in fishes and some reptiles, and that in the evolution of the higher vertebrates out of these lower forms, certain of these movable segments were rendered less movable with respect to each other by the mechanical conditions to which the successive generations were exposed, until at length the sacrum was formed, is undoubtedly a theory that excludes all design of an infinite artificer, and all intention whatever. It is a theory which relegates the most special contrivances and the most exact adaptations to the fortuitous operation of causes that could not have produced the variations of structure and at the same time have preserved the typical uniformity. It is certainly a theory which we should not apply to the works of man, if we were investigating products which seemed to be the result of human ingenuity and skill, but of the origin of which we had no direct evidence. In such a case, we should not shut our eyes to the proofs of intentional variations and adaptation, or, if we did, our speculations would not be likely to command the assent of cultivated and sound reasoners. We may treat the works of Nature by a system of logic that we should not apply to the works of man, but if we do, we shall end in no tenable results. The principal and in fact the only essential distinction to be observed between the works of Nature and the works of man relates to the degree of power, intelligence, and skill in the actor. If we assume, as we must, that in the one case there was an actor, applying will, intelligence, and power to the properties of matter, and molding it into certain products and uses, and that in the other case there was no actor, but that all products and results are but the ungoverned effects of what are called natural laws in contradistinction to all intentional purposes, we must argue upon principles that are logically and diametrically inconsistent in themselves, and at variance with fundamental laws of reasoning.

I will now advert to an omission in Mr. Spencer's analysis of the sacrum, which overlooks one of the strongest proofs of intentional design afforded by that part of the spinal column. We have seen what was its general purpose and growth, and the process of its formation. We have now to note its variations in the male and the female skeleton. In the male, the sacrum, thus formed before birth, after birth answers to and performs its ultimate function of a comparatively rigid and inflexible piece of bone, and it is provided with no other special characteristic. In the female, on the contrary, there is a most remarkable adaptation of this piece to the function of maternity. While all the upper vertebrÆ of which this piece was originally composed are welded together after birth in the female as in the male, in the female the lowest segment of all remains for a certain time flexible relatively to the upper part of the sacrum, in order to admit of the necessary expansion of the pelvis during the passage of the infant from the womb of the mother. In the normal condition of females of all the vertebrate orders, this flexibility of the lower part of the sacrum continues while the period of possible maternity continues. If in any individual female it happens to be wanting during the period of possible conception, delivery can not take place without danger to the mother or the offspring, or both. Hence, in very bad cases, nature has to be assisted by extraordinary means. But in the normal condition of the female sacrum, this flexibility, so essential in the process of safe delivery, is always found, and its special purpose is known to every anatomist, while it has no existence in the structure of the male. Is this distinction to be accounted for by the same kind of reasoning that undertakes to account for all the other great distinctions between the related forms of male and female, which reproduce their kind by a common process of the sexual union, namely, that this division of male and female came about by a habit that resulted now in the production of a male and now in the production of a female, from tendencies that were ungoverned by any special purpose? Must we not conclude, however inscrutable are the causes that determine the sex of a particular infant, that the sexes themselves were specially ordained? And if they were specially ordained, how are we to account for the special construction and function of each of them, without the interposition of a special design? And when we find a structure in the female obviously designed for a special purpose, and not existing in the male, are we to conclude that some particular race of females, in some remote period of antiquity, among the countless generations of the vertebrata, found that this flexibility of the sacrum would be highly convenient to them, and, having adopted it as a habit, transmitted it, as a specially acquired peculiarity of structure, to their female descendants? This is all very well as a theoretical speculation, but as a speculation it is entirely defective, because it assigns the peculiarity of structure to a cause that could not have produced it. On the other hand, the hypothesis of its special creation assigns it to a cause that could have produced it, and its existence is among the highest of the multitudinous evidences of intentional design and special formation.

Wherein consists the irrationality of the hypothesis that a plan of construction was intentionally, and with supreme skill, framed for very different beings, to answer in each of them a common purpose? The asserted irrational character of this hypothesis consists in nothing but a denial that there was a Creator. It comes down to this, if it comes to anything: because, if we assume that there was a Supreme Being who took any care whatever of the complex and manifold product that we call nature—if we suppose that he ordained anything—we must suppose that his power to construct was boundless, and that a repetition of his plans wherever they would be useful, to answer the beneficent and diversified ends of infinite skill and benevolence, is just as much in accordance with the whole hypothesis of his attributes as it is to suppose that he caused anything whatever to exist. If we deny his existence, if we can not satisfy ourselves of it at all, if we suppose that nothing was ordained, nothing was created, but that all these diversified forms of animal organisms grew out of a protoplasmic substance, and that there was never any absolute commencement of organic life on the globe, or any absolute commencement of anything whatever, it is of course idle to speculate upon the adoption or preservation of patterns, as it is equally idle to pursue the theory of evolution through stages which at last end nowhere whatever.[84]

It may be well to cite Mr. Spencer's final summary of the general truths which he claims to be revealed by morphology, because it will enable the reader to see just where the logical inconsequence of his position occurs: "The general truths of morphology thus coincide in their implications. Unity of type, maintained under extreme dissimilarities of form and mode of life, is explicable as resulting from descent with modification; but is otherwise inexplicable. The likenesses disguised by unlikenesses, which the comparative anatomist discovers between various organs in the same organisms, are worse than meaningless if it be supposed that organisms were severally formed as we now see them; but they fit in quite harmoniously with the belief that each kind of organism is a product of accumulated modifications upon modifications. And the presence, in all kinds of animals and plants, of functionally useless parts corresponding to parts that are functionally useful in allied animals and plants, while it is totally incongruous with the belief in a construction of each organism by miraculous interposition, is just what we are led to expect by the belief that organisms have arisen by progression."[85]

Without expending much criticism upon the phrase "miraculous interposition," as a description of what takes place in special creation, it is sufficient to say that the act of special creation of a distinct organism is to be first viewed by itself, as if it stood alone in nature, and that it is like any other act of causing a new thing to exist which did not exist before. To this idea should be added the fact that in the creation of an animal organism there is involved the direct formation of a peculiar type of animal, with a capacity of producing other individuals of the same type through a process of generation. When, after having attained this conception of the act of special creation, and contemplated a single instance of the supposed exercise of such a power, we extend our inquiries, we find many other instances of the exercise of the same power; and then we observe a certain unity of type in some peculiarity of structure, maintained under extreme dissimilarities of form and mode of life. How, then, is this one similarity of pattern, amid such multiformity in other respects, "worse than meaningless," if we suppose that "organisms were severally framed as we now see them"? The very hypothesis that they were so severally framed carries in itself a meaning which can not be thus summarily ignored; because that hypothesis implies a power in the Creator to do just what we see. You may deny the power; but if you admit the existence of the infinite creating power, you are remitted to the inquiry into its probable methods; and you can no more say that the special creation of distinct organisms, with a certain unity amid a great multiformity, leaves the whole phenomena without a meaning, than you can say that any method which you can suggest is necessarily the only method which will afford a rational meaning in what we see. You must go the length of denying the entire postulate of a Creator, before you can be in a situation to deny the meaning that is involved in the idea of creation; for that idea implies an absolute power to apply a uniform pattern of structure to a whole class of organisms varied in all other respects. The theory that each kind of organism is a product of accumulated modifications upon modifications, without any special interposition to produce the modified and distinct forms, must be maintained on one of two suppositions: either that at some period there was an absolute commencement of organic life in some form, upon this globe, and that then all the other forms which we see were left to be evolved out of that one by the ungoverned accumulation of modifications upon modifications, or else that there was never any absolute commencement of organic life at any time, but that matter, by some peculiar property derived from some source that is not suggested, took on combinations which resulted in some crude form of animated organism, and that then the accumulations of modifications upon modifications followed from some process of generation by which the successive organisms became multiplied and varied. Of the former supposition, I understand Mr. Darwin to have been a representative naturalist. Of the latter, I understand Mr. Spencer to be an advocate. Upon what may be called the Darwinian doctrine, the idea of a Creator, causing to exist at some time some crude form of animal life, is admitted. Upon the Spencerian doctrine, which will be in this respect more closely examined hereafter, I do not see that the idea of a creating power comes in anywhere, either at the commencement of a series of organisms or at any point in that series. But, upon the logical proposition asserted in the passage last above quoted, it is obvious that, unless the idea of a Creator is absolutely denied, the presence of a unity of type amid any amount of dissimilarities of form and mode of life can not be pronounced to be without meaning, because the idea of a Creator implies a power to make that very unity amid the uniformity, which is asserted to be inexplicable without resorting to the theory that it was not made at all, but that it grew out of events over which no superintending or governing power was exercised. Upon this kind of dogmatic assertion there can be no common ground of reasoning.

The assumed incongruity between the facts and the hypothesis of a special creation of each organism is an incongruity that arises out of the assumption that such special creation was an impossibility. If once the idea of an infinite creating faculty is assumed as the basis of the reasoning, all seeming incongruity vanishes, and the probable method of that creating power must be determined by the preponderance of evidence. If the power is denied, we must grope our way through systems which impute everything to the properties of substance, without any suggestion of a source from which those properties were derived, and without anything to guide them but the tendencies implanted in them, we know not how or when, and of the origin of which we have not even a suggestion. Some of the speculations of Greek philosophers adverted to in a previous chapter may serve to show us what comes of the omission to conceive of power as abstracted from substance or its properties. The philosophy which first attained to this conception led the way to that conception of an Infinite Being, without whose existence and attributes all speculation upon the phenomena of nature leads to nothing. A belief in his existence and attributes must undoubtedly be attained by an examination of his works, if we set aside the teachings of revealed religion. But if we can not attain it, we have no better means for believing in the doctrine of evolution than we have for believing in any other method by which the phenomena of nature have become what they are.

The question here is, not whether descent of organisms from organisms, with modifications upon modifications, is a supposable theory, but whether it is so satisfactorily shown that it can be said to exclude the hypothesis of a special creation of each organism. There may be parts of structure in one animal which seem to have no functional use, although we should be cautious in making the assumption that they are of no use because we have not yet discovered that use. But let it be assumed that these apparently useless parts in one animal correspond to parts which in another animal are functionally useful. If there was established for these two separately created animals a like system of procreation and gestation, that system, affected at the same time by a law of growth imposed by the special type of the species, might in one species lead to the presence of parts of which we can not recognize the use, and might in other species lead to the presence of parts of which we can see the use. It does not help to a better explanation to say that there has been an accumulation of modifications upon modifications in the course of an unknown descent of one organism from another. Why did these modifications stop short of the production of a species or of several species in which no resemblance of parts more or less functionally useful could be found? The supposition is that the modifications have been going on through millions of years. Time enough, therefore, has elapsed for the destruction of all uniformity of structure; and the causes of modification are as immeasurable as the period through which they are supposed to have been operating. The imaginary ancestral stock, wherever it is placed in the line of remote descent, had, in its first distinctive existence, a peculiar structure, which it bequeaths to its offspring. In the countless generations of its descendants, modifications of that structure take place, until a new animal is evolved. What preserved any unity of type from the modifying influences? It was not choice on the part of the several descending species; not a conscious exertion to preserve something; it was nothing but the propinquity of descent, which by the law of heredity transmitted certain resemblances. But why was that law so potent that it could preserve a certain unity of type, and at the same time so powerless as not to prevent the modifications which the successive organisms have undergone in all other respects? Or, to reverse the terms of the question, why were the causes of modification sufficiently powerful to produce distinct species, and yet not powerful enough to eliminate the resemblances which we find obtaining throughout the whole group of animals to which these several species belong? It would seem that here we are not to lose sight of the fact that, in the animal kingdom, procreation never takes place between a male and a female of distinct species, and that we have no reason to believe that it ever did take place. Now, although the evolution hypothesis supposes that, starting from an ancestral stock, the modifications of structure have been produced in offspring descended from parents of that same stock, which have transmitted acquired peculiarities to their immediate progeny, and so on indefinitely, yet there must have been a time when the diverging species became distinct and peculiar organisms, and when it became impossible for any crossing of these organisms to take place. All the supposed modifications, therefore, have taken place within the limits of an actual descent of one kind of animal from another, each successive pair belonging to the species from which they were individually generated. In this descent of lives from lives, there came about changes which in progress of time led to two animals as wide asunder as the man and the ostrich, or as the man and the horse, and yet the causes which were powerful enough to produce these widely diverging species were not powerful enough to break up all unity of plan in some one or more respects. If naturalists of the evolution school would explain how there has come to be, for example, in the skeleton of the vertebrata, a bony structure called the spine, in which a certain resemblance and a certain function obtain throughout the whole class, and yet one species creeps upon its belly, another walks on four legs, and another on two, and one flies in the air and another never can do so, and how this could be without any design or special interposition of a creating power, but that the whole of this uniformity amid such diversity has arisen from acquired habits among the different descendants from an aboriginal stock that had no such habits in either mode of locomotion, and no organs for such modes of life, they would at least be able to commend their theory to a better appreciation of its claims than is now possible to those who want "grounds more relative" than a naked hypothesis.

3. The argument from embryology requires for its appreciation a careful statement of its abstract proposition, and a statement of it in a concrete form. As an abstract proposition, embryology, or the comparison of the development of different organisms under their embryonic stages, shows that in the earliest stage of any organism it has the greatest number of characters in common with all other organisms in their earliest stage; that at a later stage its structure is like the structures displayed at corresponding phases by a less extensive number of organisms; that at each subsequent stage the developing embryo becomes more and more distinguished from the groups of embryos that it previously resembled; and that this divergence goes on, until we reach the species of which the embryo is a member, in which the class of similar forms is finally narrowed to that species.

It seems that Von Baer formulated this generalization of embryologic development into an "embryologic law," which, according to Mr. Spencer, becomes a support to the hypothesis of evolution in this way: Species that had a common ancestry will exhibit a parallelism in the embryonic development of their individual members. As the embryos of the ancestral stock were developed in their growth, so the embryos of the descended species would be developed at corresponding phases in a similar way. As one species diverged from its ancestral stock, there would come about modifications in the development of its embryos, and thus a later ancestral stock would be formed, which would in turn transmit to its descendants in the development of the embryo less and less resemblances, and so on, until finally the individual animal, at birth, would structurally resemble only the individual infants of its own race.

Here, then, is another remarkable instance of the force of an adopted theory. First, we have a comparison of the embryonic development of different animals from their seminal germs which displays certain phenomena of resemblances and departures. Next, we have the assumption of an ancestral stock, the common origin of all the organisms in the development of whose embryos among its descendants an embryologic law was to work, starting from the visible resemblance of all the germs, then exhibiting structural changes into later ancestral stocks, and so on, until the resemblances are reduced to those which obtain only among individuals of the same species. So that, without the hypothesis, the assumption of an ancestral stock of all the organisms, formed somehow in the course of descent from a germ that gave rise to an animal of some kind, we have nothing to which to apply the embryologic law. We are to infer the embryologic law from the parallelism of embryonic development which prevails in the whole series of animal generation, or from its divergences, or from both, and then we draw from this law the inference that the whole series of animals came from some common stock. The difficulty with this whole theory is, as I have more than once suggested, that we have no means, aside from the theory itself, of connecting lives with lives, in the generation of one distinct species out of another. Without some proof of the fact that the human foetus was a diverging growth out of some ancestral stock that was the same as that from which the foetus of another animal was a different diverging growth, the embryologic law is no help to us whatever. If this kinship of the human foetus with the foetus of some other animal can not be found, by tracing the intermediate links which carry them respectively back to their common ancestor, between what animals in respect to their embryonic development can such kinship be found, excepting upon the theoretical assumption of a common origin of the whole vertebral class? If there was such a common ancestral stock, where is it to be placed, what was its character, when did the law of embryologic development begin to operate upon its descendants? Until some facts can be adduced which will have a satisfactory tendency to show the kinship of one animal with another by reason of ancestral descent from a common ancestral stock that was unlike either of them, the phenomena of embryologic development have no tendency to displace the hypothesis of special creations; for, on the latter hypothesis, the phenomena of resemblances and differences in the growth from the germ into the foetus and from the foetus into the newly born infant, evinced by any range of comparison of the different species, would be the same. If man was a special creation, and one of the higher quadrumana was also a distinct and separate creation, the establishment for each of a like process of procreation and gestation would produce all the resemblances of foetal growth that obtain between them, and the ordained differences of their animal destinies would explain all the divergences. Let us see if this is not a rational conclusion.

It is exceedingly difficult for the common reader of such a work as that of Mr. Spencer, on which I am now commenting, to avoid the influence of the perpetual assertion that facts are explicable upon one hypothesis alone. At each step in the argument, the array of facts terminates with the assertion that, upon the hypothesis of design, the facts are inexplicable; and yet we are furnished with no reasoning that has a tendency to show that the facts necessarily exclude the hypothesis of design, or, in other words, that the facts are inconsistent with that hypothesis. It is essential to understand what is the true scope of the hypothesis of special creation; for, without a definite idea of what that term implies, we have no proper means of comparing the facts of animal resemblances or differences with the rationality of the hypothesis that they resulted from an intentional design. Recollecting, then, that we are now pursuing the resemblances and divergences that are found in a comparison of the embryologic development of different species of animals, let us endeavor to understand the meaning of what I have suggested at the close of the last preceding paragraph; namely, the establishment for a large class of animals of a like general system of procreation and gestation, and the ordination of different destinies for the different species of animals belonging to that class. I have said that the two branches of this hypothesis would account for the resemblances in the embryological growth of different animals, and would explain the divergences which obtain among their embryological developments. The first inquiry is, whether this hypothesis presents a true philosophic idea of special creation. The next inquiry is, whether it affords a satisfactory explanation of the phenomena of comparative embryologic development.

We must never lose sight of the one grand postulate of an infinite Creator. This postulate must be conceded to the believers in special creations, because any idea of creation implies a creating power. If we conceive of creation without a Creator, we must stop all argument. Now, the hypothesis of creation, as I have more than once said, implies a being of boundless faculties. There can be absolutely no limitation to the power of such a being, either in respect to the methods by which he will accomplish his objects, or to the number and variety of these objects, or to the purposes for which they are to exist. If we narrow our conception of creating power to anything less than an infinite faculty; if we suppose it to be restricted in any direction; if we argue about it as if there were things that it can not do, we shall be without the means of reasoning soundly upon anything that it is supposed to have done. It is quite otherwise when we are reasoning about the operation and effect of secondary causes. There is no secondary cause—no imaginable operation of a fixed quality of substance—no action of any of the properties of substance—that is not limited. The scope of its action may be very wide; within its sphere it may be enormously potent; but in its very nature it is bounded.[86] It is not so with the First Cause of all things; not so with the Infinite Power which, upon the hypothesis of a First Cause, has established all the physical laws of the universe and all the properties of matter. So that, when we reason about the methods of that infinite creating power, if we find a general system established, or a pattern repeated through a very large class of organisms, the proper inference is, not that the power was limited, but that it has been exercised to the whole extent of what was useful, and in that direction has been exercised no further; and if we find variations or additional structures incorporated with the repetition of a general pattern, the proper inference is that the unlimited creating power has put forth all the additional exertion and skill needful for the formation of new beings.

What, then, does the establishment of a like system of procreation and gestation imply, upon the supposition of the distinct creation of species? It implies a certain parallel embryonic development, from the germ to the foetus and from the foetus to the new-born infant, throughout a large group of different animals; and this parallelism would in certain stages of the embryonic growth display identity or close similarity of form and structure. But as in each species of animal the distinct creation would necessarily imply a distinct destiny, the parallelism of embryonic form and structure would cease at the point of development at which the characteristic structure of the species would begin to unfold itself. The general system of procreation and gestation common to a whole class of different animals, and the ordained diversity of species, would present the same phenomena of resemblances and differences in the embryonic development that are supposed to be explicable only by the hypothesis of a descent of all the species from a common ancestral stock through the process of evolution.

Notwithstanding the mystery and obscurity in which the process of animal procreation is involved—a mystery and obscurity which will perhaps never be fully solved—we can see enough to warrant some definite conclusions. One of these conclusions is that, in the formation of the germ which becomes developed into the foetus, the male and female parent each contributes some cellular substance to the compound which constitutes that germ. We may safely infer this, because the individual animal becomes a union of characteristics belonging to both the parents, although the traits that are peculiar to one of the parents may be more or less marked in their different offspring, so that in one of the descendants the paternal and in another the maternal traits will predominate. But in every descendant from the same pair there is more or less of the peculiarities of each parent plainly discernible. The inference, therefore, may be safely drawn that the male and the female parent each contributes to the formation of the ante-foetal germ some cellular substance, in which resides the typical characteristic of animal organism which each parent possesses. The compound germ that is thus formed is endowed with the mysterious principle of animal life which admits of growth and development; and whether after its formation the female parent bestows most or bestows least upon the product, that product consists of a union of cellular substances contributed by both the male and the female parent in the sexual act of procreation. This compound resultant germ, in the earliest stage of its formation, like the separate cells of which it is a union, exhibits no visible difference when we compare the ante-foetal germ of one animal with that of a different animal. Perhaps we shall never be able to detect either chemical or mechanical differences in the cellular substances or in the earliest stage of the compound product which has resulted from their union. But in that compound product there resides a contributory cellular substance derived from each of the parents; and it is a just inference from this fact, and from what we learn when we trace the further development, that there is a peculiar and typical structure impressed upon and inwrapped in this compound germ, which is to grow into a foetal development by a law of its own. There will at the same time be a particular law of development for each distinct species of animal, and a general law of development for a great variety of species among whom there obtains a common process of the sexual union and of the contribution of male and female cellular substance. When the foetus becomes formed, there will still be marked resemblances in the different species, before the stage is reached at which the characteristic structure of each species is to begin to unfold itself. But at some time the fundamental difference of structure originally lodged in the cellular substances of which the compound ante-foetal germ was composed, and impressed upon that germ as the type which was gradually to unfold itself into a distinct being, will begin to exert its force. The resemblances of structure will become less and less, as the foetus of the different animals approaches to the time of birth. Organs, or appearances of organs, which at one stage of the comparison have seemed to indicate descent from a common ancestral stock, but which may have been only the result of a common process of foetal development, will be found to be varied by force of the original diversity of structure and destiny that was made to reside in the seminal substance of each distinct species of animal; and, at length, this original and intentional peculiarity of structure and being would become perfected at or before the period when birth is to take place, leaving only those resemblances which must obtain in all organisms constructed in certain respects upon a uniform plan, and brought into being by a common process of procreation and gestation.

Let us now see whether this reasoning involves any such unphilosophical or unscientific belief as is supposed. Passing by the often-repeated assertion that the facts of comparative embryologic development are reconcilable only with the belief in evolution, let us advert to some of those facts. "The substitutions," says Mr. Spencer, "of organs and the suppression of organs, are among those secondary embryological phenomena which harmonize with the belief in evolution, but can not be reconciled with any other belief. There are cases where, during its earlier stages of development, an embryo possesses organs that afterward dwindle away, as there arise other organs to discharge the same functions. And there are cases where organs make their appearance, grow to certain points, have no functions to discharge, and disappear by absorption." The concrete illustration of this substitution and suppression of organs is thus given by Mr. Spencer:

"We have a remarkable instance of this substitution in the successive temporary appliances for aËrating the blood which the mammalian embryo exhibits. During the first phase of its development, the mammalian embryo circulates its blood through a system of vessels distributed over what is called the area vasculosa, a system of vessels homologous with one which, among fishes, serves for aËrating the blood until the permanent respiratory organs come into play. After a time, there buds out from the mammalian embryo a vascular membrane called the allantois, homologous with one which, in birds and reptiles, replaces the first as a breathing apparatus. But while, in the higher oviparous vertebrates, the allantois serves the purpose of a lung during the rest of embryonic life, it does not do so in the mammalian embryo. In implacental mammals it aborts, having no function to discharge; and in the higher mammals it becomes "placentiferous, and serves as the means of intercommunication between the parent and the offspring"—becomes an organ of nutrition more than of respiration. Now, since the first system of external blood-vessels, not being in contact with a directly oxygenated medium, can not be very serviceable to the mammalian embryo as a lung; and since the second system of external blood-vessels is, to the implacental embryo, of no greater avail than the first; and since the communication between the embryo and the placenta among placental mammals might as well or better have been made directly, instead of by metamorphosis of the allantois—these substitutions appear unaccountable as results of design. But they are quite congruous with the supposition that the mammalian type arose out of lower vertebrate types. For, in such case, the mammalian embryo, passing through states representing, more or less distinctly, those which its remote ancestors had, in common with the lower vertebrata, develops these subsidiary organs in like ways with the lower vertebrata."[87]

In what way, then, are these substitutions unaccountable as results of design, and why are they any more congruous with the supposition that the mammalian type arose out of the lower vertebrate type? In the first place, it is necessary to have a distinct conception of what is meant by design. In the present case, it means that for a certain large group of animals there was established a system of reproduction by the sexual union of male and female, each contributing a cellular substance peculiar to itself, in the formation of a compound cellular substance in which the separate substances are united, and which is to be developed into the foetus by a law of growth; and as a further design there is wrapped up in the compound germ of each distinct species of animal a typical plan of ultimate form and structure. This typical plan can not be detected in the germ itself, as it is too subtile and obscure even for the microscope; but we have every reason to believe that it is there in all its distinctness of original purpose, because at a later stage of the embryonic development we find a distinct species of animal is the result. This is a conclusion that must be adopted by the evolutionist, as well as by the believer in special creations, because it has nothing to do with the question of how distinct species came to exist. Whether they were designedly and separately created, or were evolved out of one another, the reproductive process by which the individuals of the same species are brought into being alike involves the conclusion that, in the ante-foetal germ of that species, there is somehow involved, in a form so minute that it can not be seen, the type of animal which is to belong to that species, and to no other. Here, then, we have the grand and compound design which is to obtain throughout a whole group of different animals; namely, that they shall multiply in the production of individuals of their own types, by a sexual union, in which the male and the female each contributes a cellular substance of its own to the formation of a compound germ, and in that germ there is made to reside the typical form and structure of a distinct organism, so minute that we can not see it, but which we must conclude from the result has been put there to be developed by a law of growth ordained for the accomplishment of a certain distinct order of beings. But the very obscurity of this type, in the earliest stage of embryonic development, leads to the conclusion that while it will never be lost, so long as its life is preserved, it will unfold itself in ways that will be equally beyond our ken, until the point is reached where it is no longer obscured, but where it is revealed in all its distinctness of outline and its peculiarity of structure. What is certain and invariable is, that the type peculiar to the species is at some time in the growth of the individual animal perfectly developed. But in the modes of its development through different embryonic stages, there will be variations and substitutions of organs in the different species, but in each distinct species these variations and substitutions will be uniformly the same, because the law of development imposed by the distinct type, while it may operate differently among different species, will always operate in the same way in the same species. Thus in one animal the development from the original type which was implanted in its seminal ante-foetal germ may at one stage exhibit an organ for which at a later stage another organ will be substituted; and in another animal a seemingly corresponding organ may serve a different purpose, or may altogether abort. These embryologic phenomena, varying in different species, but occurring uniformly in the same species, are necessarily among the most obscure of all the phenomena of animal life, on account of the fact that they take place where we can not watch the changes or modifications as they are taking place during actual foetal life. But they are no more explicable upon the hypothesis of the descent of distinct animals from a common stock, than they are upon the hypothesis of distinct creations of species. Upon the former hypothesis, the assumed propinquity of descent implies the preservation of the same mode of embryonic development until it becomes varied by the operation of causes that bring about a new habit of development, and then a fixation in this new habit after a new species or a new ancestral stock is formed; so that in each distinct species there comes at length to be a uniform process of substituting and suppressing organs, or changing the functions of organs. But how are we to account for the operation of causes that have preserved a parallelism of development, along with the operation of causes that have produced the different modes of development, when all the species are supposed to be derived from a common ancestral stock, which first began to procreate and to develop its descendants in one and the same way? What are the facts which will enable us to say that the mammalian type arose out of the lower vertebrate types, when we compare the different modes of their embryologic development? How are we to estimate the chances for a preservation of so much resemblance as exists between the two in their embryologic lives, and the chances for the variations that are observable? What we can safely conclude is that there is a law which holds each species in a constant repetition of its own foetal growth, according to its unvarying development in the same series of changes, substitutions, or suppressions. But we can not safely conclude that this species became formed in the supposed process of descent from a remote ancestral stock, which may or may not have originally exhibited the same series of changes, substitutions, or suppressions. If the ancestors of the mammalian vertebrates were the kind of animal supposed, we have to find, in order to justify the supposed descent, those states which represent the correspondence between the mode in which the ancestral stock developed its own embryos, when compared with the mode in which the type of the lower vertebrata developed its embryos, so as to make it reasonably certain that these subsidiary organs derived their several substitutions or suppressions from the process of descent, and not from any special mode of development ordained for each distinct species. We may imagine these states through which the mammalian embryo has passed, but as yet we have only a theory which suggests their existence without facts to support it. The truth would seem to be that this whole subject of comparative embryology, upon the hypothesis of the kinship of all organized beings, or the descent of many distinct species from a common stock, is involved in very great difficulties; not the least of which is the difficulty of explaining how the diverging descendants from that stock came to be endowed with habits of embryologic life and growth that resulted in the production of very different modes of development, and at the same time preserved for each new species its own peculiar mode of development. To say, for example, that the mammalian embryo passed through states representing, more or less distinctly, those which its remote ancestors had in common with the lower vertebrata, and that it developed certain subsidiary organs in like ways with the lower vertebrata, is merely to state a theory, which, without some evidence that the mammalian embryo was a formation resulting from a connection of lives with lives back to a common ancestor whose embryo was developed as those of the lower vertebrata are, amounts to nothing. Often as this want of evidence has been adverted to, it must be here again pointed out: for the whole argument from embryology, like that derived from a comparison of the forms of mature animals, lacks the support of facts that are essential to show the connection of life with life which descent from a common ancestral stock necessarily implies.

On the other hand, the hypothesis of the distinct creation of different species deals with the phenomena of embryologic life in a very different way. It supposes the creation of a pair, male and female, and a law of procreation, designed for the multiplication of individuals of a fixed type. It supposes many such creations, each having in its own peculiar germ the characteristic type of organism that will distinguish the mature animal from all the others. It supposes finally a law of development common to all the species the individuals of which are multiplied by the sexual union of male and female; a law of growth under like conditions, which leads to a parallelism of development until the typical plan of form and structure designed for each distinct animal, and implanted in its germ, begins to take on a mode of development peculiar to that species, and at length the perfect individual of that species is the result. In this hypothesis, therefore, there is no necessity for resorting to any connection with an imaginary ancestral stock of a different type, or for resorting to a theoretical process by which successive generations may be supposed to have gradually arisen out of the ancestral stock by successive changes which have at length resulted in a totally new species. The new species is what is supposed to have been aboriginally created, and to have been placed under its own law for the multiplication of individuals of the same type. In point of simplicity, of comparative certainty, of freedom from accidental causes of variation of which we can predicate no specific result, this hypothesis seems to have a far greater degree of probable evidence in its favor than the theory which entirely lacks the requisite evidence of intermediate connections between the lives of one species with the lives of a remote and different species. For, while it may be truly said that no man ever saw a special creation take place, and while such an act of the infinite power is of a nature that places it beyond the observation of our senses, it is neither inconceivable nor improbable, nor inconsistent with the idea of the divine attributes which we derive from the study of nature. On the other hand, it is not only equally true that no man ever saw, or in the nature of things ever can see, an evolution of distinct species out of other distinct species, but the whole nature of the supposed process of transformation involves an element of chance which forbids all calculation of the results. How, for example, in this very matter of comparative embryological development on the hypothesis of descent of all the species of the vertebrate animals from a common ancestral stock of a different type, are we to account for the fact that the embryo of any one of the descended species has come to be developed in a mode peculiar to itself and differing from the mode in which the embryo of the ancestral stock was developed? The law of sexual union, under which the individuals of the supposed ancestral stock were multiplied, must have imposed on that species an invincible necessity of reproducing in its offspring the same type that constituted the peculiar organism of the parents, whether these parents were or were not the fittest survivors of their race after the severest struggle for existence which they may have had to undergo. If the pair, or the male of that pair, has in the course of that struggle acquired a new organ, or more completely developed an old one, before the act of procreation takes place, how is it that the ovum is developed into the foetus, and the foetus into the newly born infant, in an invariable mode peculiar to the species to which the parents belonged? Why did not the same causes of variation which are supposed to have changed the ancestral type into one of a new and entirely distinct character, also vary the mode of foetal development? When and how did the new organs become fixed in the type which the parents have transmitted to the offspring? And if they became so fixed in the germ which was formed out of the cellular substance contributed by each of the parents, why do we find in every known species participating in this process of reproduction a uniform mode of embryologic development peculiar to the species, and exhibiting its own suppressions and substitutions of organs, irrespective of any newly acquired peculiarities in the individual structures of the parents?

The believer in special creations has to answer no such questions as these. His hypothesis assumes the creation of a pair of animals of a certain distinct species; a law of procreation and gestation common to a vast multitude of organisms; and a law of embryologic growth peculiar to each species. Whatever peculiarities of structure may have been possessed by the immediate parents of any individual of any one of these different species—peculiarities which did not separate the parents from their race, but only made them the fittest survivors of their race—those peculiarities would or would not descend to their immediate offspring, according to varying and very inappreciable circumstances. But that which constituted the special type of the race, and especially that which constituted its peculiar mode of development during the embryonic stage, would remain unaffected by these incidental and accidental peculiarities of the parents, because, from all that we can discover, that special type was impressed upon the embryo at the earliest stage of its existence, and constituted the living model that was to be developed into the perfect animal of that species, by a law which placed it beyond the influence of any adventitious and non-essential advantages which the male or female parent may have acquired over other individuals of the same race. So that, if the postulate of a special creation of species be assumed as the groundwork of the reasoning, we have to go through with no speculations about a common ancestral stock of all the species, and we have to account for no phenomena that are exposed to chances which might have produced very different results from those which are open to our observation, and results of which we can predicate nothing with any degree of certainty. On the hypothesis of the special creation of a species, and an aboriginal pair of each species, with all that this implies, we can with a high degree of certainty predicate most of the phenomena that we have to observe, and more especially so much of the phenomena of embryologic growth of the different species as are open to our investigation after the life of both mother and embryo has become extinct.

It only remains for me to give to this reasoning a concrete application. Take the case made use of by Mr. Spencer in the passage above cited—that of the "allantois," a vascular membrane, which is said to be in the mammalian embryo homologous with one which in the higher oviparous vertebrates, such as the birds and reptiles, replaces what was at first a breathing apparatus, and becomes for them, during the rest of embryonic life, a sort of lung, or an organ that aËrates the blood until the permanent respiratory organs come into play. In the mammalian embryo, the first appliance for aËrating the blood is described as a system of vessels distributed over the area vasculosa, and like that which is first observable for the same purpose in fishes. But, as the mammalian embryo continues to grow, a change takes place. There buds out from it the vascular membrane called the "allantois," which is substituted in the place of the first aËrating apparatus. Then a further change takes place, as between the higher oviparous vertebrates and the mammalian vertebrates. In the former, the "allantois" continues to perform the breathing function through the rest of the embryonic life. In the mammalian vertebrates it undergoes two changes: In the implacental mammals, it aborts, having no function to discharge; in the placental mammals it becomes modified into another organ, namely, that which serves to convey nutrition from the mother to the offspring. After birth, it is of course ended.

Now, the reasoning, or rather the assertion, that these substitutions are unaccountable as the results of design, appears to me to be singularly inconclusive. It is quite illogical, according to all philosophic meaning of design as applied to the works of the Creator, or to the works of nature, if that term is preferred, to argue that a particular object could have been better accomplished directly, than by a metamorphosis of an organ from one function to another, or by substitution. The metamorphosis, or substitution, which in such cases we find in nature, is of itself the very highest evidence that the indirect method was the best, if we admit the idea of a Creator, because it was the method chosen by a being of infinite perfections for reasons which we may not be able to discover, but which we must presume to have existed, if we concede that hypothesis of attributes which "design" in this case necessarily implies. But how are these metamorphoses and substitutions any more accountable upon the supposition that the mammalian type arose by generation out of the lower vertebrate types which in their embryonic life exhibited the same changes? The doctrine or theory of evolution does not account for them at all; for, while the doctrine supposes, as matters of pure theory, that there were certain states through which the mammalian embryo passed, which represented more or less distinctly those which it had in common with its assumed remote ancestors, the lower vertebrata, it does nothing more than to suggest the theoretical idea that the mammalian embryo came to develop these subsidiary organs in the mode in which they were developed in the embryo of the lower vertebrata, because it was descended from the lower vertebrata. The varying states through which the embryo passed from the lower vertebrata to the mammalian type, are all hypothetical, and there is, therefore, no basis of fact on which to rest the belief in a common mode of development, as resulting from a connection of lives with lives between the mammalian type and the types of birds, reptiles, or fishes.

On the other hand, the hypothesis of the special creation of a species implies the simple fact of a designed process of embryonic development for each species, with substitutions of organs and changes of function in certain organs peculiar to that species; a fact which may well consist in a certain parallelism in the different metamorphoses, and a preservation of the same unvarying changes in the development of each separate embryo. Why these changes should exist, we can not tell; but their existence is very strong proof that they were designed, or made to take place, for some reason, if we admit the hypothesis of a Creator. For that hypothesis, we must look to a wider class of facts, and to the whole phenomena of nature.

4. We now come to the argument from distribution. This is one of the weakest of the indirect supports of the doctrine of evolution; but, as it is much relied upon, it must be stated with all the force that it is supposed to have. The facts that are relied upon are these: When we survey the whole surface of the globe, so far as it is known to us, we find, in the first place, that the areas which have similar conditions (of soil and climate), and sometimes, where the areas are nearly adjacent, are occupied by quite different faunas. On the other hand, it is said that areas remote from each other in latitude, and contrasted in soil and climate, are occupied by closely allied faunas. The inference drawn is, that there is no manifest predetermined adaptation of the organisms to the areas, or habitats, in which they are found, because we do not find that like organisms are universally or generally found in like habitats, nor very unlike organisms in very unlike habitats. The conclusion is, that the facts of distribution in space do not conform to the hypothesis of design. In other words, the different animals found in different regions were not specially designed for those regions, but some of them have extended into regions of a different character; and when the regions are very unlike there are not found very unlike organisms, but there is a general similarity, or a less extensive variety. There is said, also, to be another important fact, namely, that "the similar areas peopled by dissimilar forms are those between which there are impassable barriers; while the dissimilar areas peopled by similar forms, are those between which there are no such barriers." Hence is drawn the conclusion that "each species of organism tends ever to expand its sphere of existence—to intrude on other areas, other modes of life, other media."[88] A good deal of aid is supposed to be derived for this argument respecting animal life by analogies drawn from the vegetable kingdom; but I can not help thinking that there is much caution to be observed in formulating such analogies into a law of universal application, or into one that relates to the existence of animal organisms. The origin, the multiplication, and the spread of animals involve a principle of life, organization and development which is very different in some important respects from that which obtains in the vegetable world. But, without laying any stress upon this distinction, and without intending to deprive the argument for animal evolution of any aid which it can derive from such supposed analogies, I pass to the specific argument respecting animal distribution. The argument is this: Races of organisms become distributed over different areas, and also through different media. They are thrust by the pressure of overpopulation from their old into new habitats, and as they diverge more widely in space they undergo more and more modifications of structure, by reason of the new conditions on which they enter. Thus, these powerfully incident forces, the new conditions on which the migrating races enter in new regions, vary the structure which they originally brought with them, and which descended to them from the common stock of which they were modified descendants. The widest divergences in space, under such circumstances, will indicate the longest periods of time during which these various descendants from a common stock have been subject to modifying conditions. There will, therefore, come to be, it is said, among organisms of the same group, smaller contrasts of structure in the smaller areas; and, where the varying incident forces vary greatly within given areas, the alterations will become more numerous than in equal areas which are less variously conditioned: that is to say, in the most uniform regions there will be the fewest species, and in the most multiform regions there will be the most numerous species. These hypotheses are said to be in accordance with the facts of distribution in space.[89]

But there are also facts of distribution through different media. The meaning of this is, that, whereas all forms of organisms have descended from some primordial simplest form, which inhabited some one medium, such as the water, its descendants, by migration into some other medium or other media, underwent adaptations to media quite unlike the original medium. In other words, the earth and the air have been colonized from the water. Numerous facts are adduced in support of this conclusion, which are thus summarized:

There are particular habitats in which animals are subject to changes of media. In such habitats exist animals having, in various degrees, the power to live in both media, consequent on various phases of transitional organization. Near akin to these animals, there are some that, after passing their early lives in the water, acquire more completely the structures fitting them to live on land, to which they then migrate. Lastly, we have closely-allied creatures like the Surinam toad and the terrestrial salamander, which, though they belong by their structures to the class Amphibia, are not amphibious in their habits—creatures the larvÆ of which do not pass their early lives in the water, and yet go through these same metamorphoses! Must we, then, think that the distribution of kindred organisms through different media presents an insurmountable difficulty? On the contrary, with facts like these before us, the evolution-hypothesis supplies possible interpretations of many phenomena that are else unaccountable. Realizing the way in which such changes of media are in some cases gradually imposed by physical conditions, and in other cases voluntarily commenced and slowly increased in the search after food, we shall begin to understand how, in the course of evolution, there have arisen those strange obscurations of one type by the externals of another type. When we see land-birds occasionally feeding by the water-side, and then learn that one of them, the water-ouzel, an "anomalous member of the strictly terrestrial thrush family, wholly subsists by diving—grasping the stones with its feet and using its wings under water"—we are enabled to comprehend how, under pressure of population, aquatic habits may be acquired by creatures organized for aËrial life; and how there may eventually arise an ornithic type, in which the traits of the bird are very much disguised.

Finding among mammals some that, in search of prey or shelter, have taken to the water in various degrees, we shall cease to be perplexed on discovering the mammalian structure hidden under a fish-like form, as it is in the Cetacea. Grant that there has even been going on that redistribution of organisms which we see still resulting from their intrusions on one another's areas, media, and modes of life, and we have an explanation of those multitudinous cases in which homologies of structure are complicated with analogies. And while it accounts for the occurrence, in one medium of organic types fundamentally organized for another medium, the doctrine of evolution accounts also for the accompanying unfitness. Either the seal has descended from some mammal which, little by little, became aquatic in its habits, in which case the structure of its hind-limbs has a meaning; or else it was specially framed for its present habitat, in which case the structure of its hind-limbs is incomprehensible.[90]

Along with these phenomena of distribution in space and in medium of life, we have the further element of distribution in time; the facts of which are admitted, however, to be too fragmentary to be conclusive either for or against the doctrine of evolution. Still it is claimed that there is one general truth respecting distribution in time, which is "profoundly significant, namely, that the relations between the extinct forms of life, found by geological exploration, and the present forms of life, especially in each great geographical region, show in the aggregate a close kinship, and a connection which is in perfect harmony with the belief in evolution, but quite irreconcilable with any other belief. As Mr. Darwin has expressed it, there is 'a wonderful relationship in the same continent between the living and the dead.'"[91]

The argument from distribution is thus summed up by Mr. Spencer:

Given, then, that pressure which species exercise on one another, in consequence of the universal overfilling of their respective habitats—given the resulting tendency to thrust themselves into one another's areas, and media, and modes of life, along such lines of least resistance as from time to time are found—given, besides the changes in modes of life hence arising, those other changes which physical alterations of habitats necessitate—given the structural modifications directly or indirectly produced in organisms by modified conditions—and the facts of distribution in space and time are accounted for. That divergence and redivergence of organic forms, which we saw to be shadowed forth by the truths of classification and the truths of embryology, we see to be also shadowed forth by the truths of distribution. If that aptitude to multiply, to spread, to separate, and to differentiate, which the human races have in all times shown, be a tendency common to races in general, as we have ample reason to assume, then there will result that kind of relation among the species, and genera, and orders, peopling the earth's surface, which we find exists. Those remarkable identities of type discovered between organisms inhabiting one medium, and strangely-modified organisms inhabiting another medium, are at the same time rendered comprehensible. And the appearances and disappearances of species which the geological record shows us, as well as the connections between successive groups of species from early eras down to our own, cease to be inexplicable.[92]

Passing by what is here said of the aptitude of the human race to multiply, to spread, to separate, and to differentiate—an aptitude which has never resulted in the production of an essentially different animal, or in anything but incidental variations within the limits of the same species—I propose now to apply to this argument from distribution a test which seems to me to be a perfectly fair one, and one which it ought to be able to encounter. If the theory that the different species of animals now known to us have been evolved successively by descent from some primordial simplest form through modifications induced by change of habitation, of medium of life, and accumulation of new structures occurring through an immense period of time, be a sound hypothesis, the process which has evolved superior out of inferior organizations ought, in consistency with itself and with all its supposed conditions, to be capable of being reversed, so as to lead to the evolution of inferior out of superior organisms. For, although the doctrine of evolution has thus far been applied only to facts which are supposed to show an ascent in the scale of being, the argument ought to be equally good for a descent in the scale of being, provided we take care to include all the elements and causes of a change of structure, mode and medium of life, and the necessary element of time, in the operation of the process. The imaginary case that is about to be put shall include all the elements of the evolutionary hypothesis, and will serve to test at least the rationality of that theory.

Let it be supposed, then, that there was a period in the history of this earth when the whole human race, however it originated, was confined to an island, thousands of miles from any other land. This race of men adapted to a life in one medium, the air, may be supposed to have so far advanced in the ruder arts of hunting and fishing, and in the higher art of tillage, as to be able for many generations to support life by what the sea and the land would put within their reach, and by the product which their rude agriculture could extract from the soil, or which the soil would spontaneously yield. But as the centuries flow on, the population begins to press upon the resources of the territory, and the struggle for life becomes very great. At length a point is reached where the supply of food from the land becomes inadequate to sustain the population, and what can be made up from the sea will not supply the deficiency. The population will then slowly decrease, but, while this decrease goes on, there comes in a disturbing cause which will prevent any adjustment of the supply of food to the diminished number of the consumers. The sea begins by almost imperceptible but steadily progressing encroachments to diminish the area of dry land; a change of climate reduces the number of other animals available for human food, and reduces the productive capacity of the earth. Then ensues that struggle for existence which is supposed to entail changes of medium of life, and to induce transformations of structure. The conditions of existence have become wholly changed. The wretched descendants of a once comparatively thriving race are dwelling on a territory which has become a marsh. They have no means of migrating to another territory; they can only migrate to another medium. They begin by feeding exclusively on what the water will afford. They pass their lives in the pursuit of a prey which lives only in the water, and in this change of life they acquire or develop organs adapted to the new condition, organs which, in such miserable reproduction of their own species as can go on, they transmit to their offspring. Modifications upon modifications accumulate in this way through untold periods of time, until at last a new aquatic or a new amphibious creature is formed, and the difference between that creature and his remote ancestral human stock is as great as that between man and the seal, or between man and any fish that swims. Still, there will be peculiarities of structure retained, which might lead any inhabitant of another world, alighting on this globe and undertaking to trace the origin of this new creature, to the supposition that he was akin to a race of men whose fossil remains he might find buried in some stratum beneath the marsh which was the last habitat of this unfortunate race, when it had all the characteristics of its original type.

Is it conceivable that this transformation could take place? Could such a condition and situation result in anything but the utter extinction of the human race, or, in other words, in an absolute break? Could there be any modifications exhibited by the last survivors of that race other than those which are familiar to us among the varieties of the human species which have never separated themselves from their race, and between whom and their ancestral stock, wherever it was originally placed on this globe, we recognize no fundamental difference of structure, whatever may have been the changes of habitat or conditions of life? Yet the conditions and elements of this imaginary case, which is simply the process of evolution reversed, are just what the evolution theory assumes as the causes of that modification which proceeds from a lower to a higher organism; and whatever may be said of the tendency, through "the survival of the fittest," to evolve higher out of lower forms of animal life, if we allow time enough for the process, there is no reason, in the nature of things, why corresponding conditions should not lead to a degradation as well as to an elevation in the scale of beings. There is, however, one reason why no such potency should be ascribed to the conditions, either in respect to the one result or the other. That reason is that all such causes of modification, either in the ascending or the descending scale, are so limited in their effects that distinct beings can not be rationally predicated as their product, whereas the power of the Infinite Artificer to give existence to distinct beings is absolutely without limit. If naturalists would turn their attention to the limitations upon the power of all such causes as those which are supposed to work in the process of evolution, and would give us the explanations to which those limitations point, in those cases of local variation which are exhibited by animals that can clearly be traced to a parent form, they would not be compelled to resort to a sweeping theory that refuses all force to any hypothesis but its own.

But now let us go a step further in this imaginary case. Let us suppose that after this new creature, fish or amphibian, descended from the human race, has inhabited the water surrounding the ill-fated island for a million of years, another great change takes place. The water begins to recede from the land by gradations as slow as those by which in the former period it encroached. The land rises from the low level to which it had sunk, by volcanic action. Forests spring up upon the sides of mountains. The soil becomes firm; verdure overspreads the fields; the climate grows genial; the wilderness blossoms as the rose. Allow another million years for this restoration of the territory to an inhabitable condition. Slowly and in an unbroken series of generations the aquatic creatures, descended from the ancient human inhabitants of the island, emerge from the sea and betake themselves to the land. Modifications upon modifications accumulate, new organs are acquired; the survival of the fittest perpetuates them; the animals ascend in the scale of being, until the human type is again evolved out of the degraded descendants of the population which two millions of years previously dwelt as men upon the island, and carried on in some primitive fashion the simpler arts of human life. Is not this just as supposable as the evolution of the human race out of some lower form of organism? Are not all the elements—time, migration from one medium to another, change of conditions, and what is supposed to lead to the production of different organisms—just as powerful to produce the inferior out of the superior as to produce the superior out of the inferior, and so on interchangeably? The answer in each case is, that all such causes of modification in the animal kingdom are limited; that when once a distinct species is in existence, we have no evidence that it loses its distinct type or merges itself in another, although the earth may be full of evidence that types which formerly existed are no longer among the living organisms.