The germ plasm is a most interesting and remarkable substance. It must be interesting, for everything which relates to life and reproduction is interesting. It must be remarkable, for out of it, under proper conditions, remarkable results are produced. Although our knowledge of its nature is very imperfect, yet let us not on this account refuse to try to understand what little is known.

In the first place, the germ plasm of animals which reproduce sexually is composed of two germ plasms—that of the male, and that of the female. That of the male is called the spermatozoon (pronounced sper´ma-to-zoÖn). It is sometimes called spermatozoid; the plural is spermatozoa. It is exceedingly small, the smallest of any cell in the body, and has the power to move from place to place. These cells are produced in enormous numbers, and so far as they have been observed under the microscope they differ considerably in power of movement and in perfection of development. Considering their small size, they must make a very long journey to find the ovum; and if they were only few in number, they would rarely succeed; but existing in large numbers, for there are millions of them produced in each sexual act of the male, some of them are pretty sure to do so, and, probably in most cases, it would be those most vigorous and capable of making the journey most direct and in the least time.

That of the female is called the ovum, or egg; plural, ova. Only a small number are produced, when compared with the number of the male spermatozoa, but there are quite enough for the ends they are to serve. They have not the same power of movement, though they do move somewhat as the amÆba does. They are also very much larger than the male cells.

The eggs of all mammals look alike as they come from the ovaries, but take on some changes afterward. HÆckel says: "Every primitive egg being an entirely simple, somewhat round, moving, naked cell, possesses no membrane, and consists only of a nucleus and protoplasm. These two parts have long borne distinctive names: the protoplasm being called the vitellus, or yelk, and the nucleus the germinal vesicle (vesicula germinativa)." The same author also says: "The human egg cannot be distinguished from that of most other mammals, either in its immature or in its more complete condition. Its form, its size, its composition, are approximately the same in all. In its fully developed condition it has an average diameter of one-tenth of a line—about the one hundred and twentieth part of an inch. If the mammalian egg is properly isolated, and held on a plate of glass towards the light, it appears to the eye as a very fine point. The normal eggs of most of the higher mammals are of almost exactly the same size. They have the same spherical form; always the same characteristic covering; always the same clear, round germinal vesicle with its dark germinal spot. Even under the highest power of our best microscopes there appears to be no essential difference between the eggs of a human being and that of the ape, the dog, the cat or other animal." This similarity is one of appearance only. There is a difference, and of this I shall speak later. It may be asked if the egg of a bird is the same as the egg of a mammal. The mature bird's egg, as it is laid in the nest, differs materially from that of any mammal; but in its miniature form, as found in the hen's ovary, it is also the same. The egg of a bird after it leaves the ovary, and as it passes along the oviduct, takes on secretions in its passage which it converts into yelk, and afterwards a shell is added to give it protection in the external world, where it must undergo incubation before it can become a bird; but before it takes on its shell it has been fertilized, and this also causes other changes. HÆckel says: "After the ripe egg of the bird has left the ovary, and has been fertilized in the oviduct, it surrounds itself with various coverings which are secreted from the inner surface of the oviduct. The thick layer of transparent albumen first forms round the yellow yelk; this is followed by the formation of the outer calcareous shell, within which is another envelope, or skin. All these coverings and additions which are gradually formed round the egg are of no importance to the development of the embryo; they are parts which have nothing to do with the simple egg cell. Even in the case of other animals we often find large eggs with thick coverings. For example, the shark's; but even in this case the egg is originally exactly similar to those of mammals when in its primitive condition as it comes from the ovary. In the case of the bird these additions serve only as food for the growing embryo, which, in the case of mammals, is furnished by a stream of the mother's blood, making 'stored-up' nutriment unnecessary."

Before, however, we can have true germ plasm the mother cell must be fertilized by the male cell. This is true of all the higher plants and animals. There are some low plants and animals in which fertilization by the male cell is not required. This has been called virginal generation. In no mammal is this possible. How fertilization takes place and what it signifies are both important questions which have not been entirely settled, and it almost seems as if they could not be settled in some of their details, except in the lower forms of life. Nature has so protected the process from observation in the higher animals that it cannot be studied in detail; but in plants and the lowest animals it has been observed with some success, and we may infer that the process is very much the same in the higher animals.

HÆckel, in his great work on the Evolution of Man, tells us that "The process of fertilization in sexual generation depends essentially on the fact that two dissimilar cells meet and blend. In former times the strangest views prevailed with regard to this act. Men have always been disposed to regard it as thoroughly mystical, and the most widely different hypotheses have been framed to account for it. It is only within a few years that closer study has shown that the whole process of fertilization is extremely simple, and entirely without special mystery. Essentially, it consists merely in the fact that the male sperm-cell coalesces with the female egg-cell. Owing to its sinuous movements, the very mobile sperm-cell finds its way to the female egg-cell, penetrates the membrane of the latter by a perforating motion, and coalesces with its cell material.

"A poet might find in this circumstance a capital opportunity for painting in glowing colors the wonderful mystery of fertilization; he might describe the struggles of the 'seed animalcules' eagerly dancing round the egg-cell shut up in its many coverings, disputing the passage through the minute pore-canals of the chorion, and then of purpose burying themselves in the protoplasm of the yelk mass, where, in a spirit of self-sacrifice, they completely efface themselves in the better 'ego.' But the critical naturalist very prosaically conceives this poetical incident, this 'crown of love,' as the mere coalescence of two cells! The result of this is, that in the first place the egg-cell is rendered capable of further evolution, and, secondly, that the hereditary qualities of both parents can be transmitted to the child."

By coalescence is understood, growing together, not mingling as water and milk might when mixed. More recent observations indicate that during coalescence both the male and female cells throw off some portions of their substance. It is also considered that the important part of each cell is its nucleus. In it all hereditary characteristics are stored up. If the nucleus be absent in either cell these cells cannot reproduce. In unicellular, or one-celled, organisms, it has been found in multiplication by division, a part of the nucleus must go with each half, otherwise the half without a part of it does not grow. In experiments in laboratories, artificial division of simple organisms may be made, and each fragment will become a perfect creature if only a very small piece of the nucleus goes with the separated portion; but if a part is cut off without any of the nucleus, then, while it may live on for a short time, it can not grow or propagate.

Possibly we have here an explanation of some hereditary phenomena in human beings. If there is an unequal division, and more of the male than of the female nucleus, the child might, as a result, inherit more of the father's than of the mother's characteristics, or the reverse.

What has been so far said about the germ plasm has been to enable the reader to possess a degree of intelligence on the nature of fertilization, so far as it is known; but from a practical standpoint the most important knowledge for those prospective parents who wish to practice intelligent stirpiculture is to understand that the health of the germ plasm or fertilized ovum depends on the health of the parents. By health, I mean the possession of a good constitution, to which will be added a strong hold on life, power to do and to endure, and quickly to recover from weariness. Disease will be easily warded off in such persons, so that there will be generally good health. Such a condition of body is usually inherited. It depends on the possession of a large supply in the body of living matter—firm muscles, a good heart, lungs and digestive organs. Those who are feeble cannot endure much; whose heart, lungs and digestive organs are weak; whose hold on life is slight, can rarely endow their offspring with these high qualities. Their children may live if no great strain comes upon them; but if they must take an active part in the struggle and competition going on in the world they cannot endure it. Mr. Spencer puts the case very aptly in his work on Ethics where he says: "It results that where maternal vigor is great, and the surplus vitality consequently large, a long series of children may be borne before any deterioration in their quality becomes marked; while, on the other hand, a mother with but a small surplus may soon cease altogether to reproduce. Further, it results that variations in the state of health of parents which involves variations in the surplus vitality have their effects on the constitutions of offspring to the extent that offspring borne during greatly deranged maternal health are decidedly feebler. And then, lastly and chiefly, it results that after the constitutional vigor has culminated, and there has commenced that gradual decline which in some twenty years or so brings absolute infertility, there goes on a gradual decrease in that surplus vitality on which the production of offspring depends, and a consequent deterioration in the quality of such offspring. This which is a priori conclusion is verified a posteriori.

"Mr. J. Mathews Duncan, in his work on Fecundity, Fertility, Sterility and allied topics, has given results of statistics which show that mothers of twenty-five bear the finest infants, and that from mothers whose ages at marriage range from twenty to twenty-five years there come infants which have a lower rate of mortality than those resulting from marriages consummated when the mothers' ages are smaller or greater. The apparent slight incongruity between these two statements being due to the fact that whereas marriages commenced before twenty and twenty-five cover the whole of the period of highest vigor, marriages commenced at five and twenty cover a period which lacks the years during which vigor is rising to its climax and includes only the years of decline from the climax."

This quotation from Mr. Spencer needs a qualifying remark. Mr. Galton, in his work on Hereditary Genius, found that the average age of mothers of men of the greatest ability was about thirty, and of their fathers thirty-five. In such cases, the physical and intellectual strength must have been above the average, and, consequently, it continued to a more advanced age. Besides, those of great ability mature later. It may also be added that Duncan's statistics, quoted by Spencer, are average statistics gathered from tables of mortality, and include every class of persons. Now, average statistics do not apply to individual cases, and they would not apply to those highly endowed physically and intellectually.

Further, those who are well endowed at birth and whose lives are in accordance with hygienic law, that is, those who do not squander their physiological resources by sensuality, by intemperance, or by excesses of any sort retain their health to a greater age than those whose lives are the reverse. Such are of a youthful physiological age, which is not altogether determined by the actual number of years they have lived, but by very high physiological conditions.

From all this we conclude that a very important rule in the production of offspring, if we would have those offspring superior, is to maintain a high degree of health—a condition in which there is a surplus of physiological capital to produce children with endowments equal to, if not superior to, their parents.

Another subject requires treatment here. It is the effect of alcohol on offspring. We are yet lacking in statistics giving the facts we need to know on this subject; but the general observation of competent persons who have had good opportunities to study it may teach us something. Alcohol, in its circulation in the blood, penetrates every part; not even the germ plasm escapes. Demme studied ten families of drinkers and ten families of temperate persons. The direct posterity of the ten families of drinkers included fifty-seven children. Of these, twenty-five died in the first weeks and months of their lives; six were idiots; in five a striking backwardness of their longitudinal growth was observed; five were affected with epilepsy, and five with inborn diseases. Thus, of the fifty-seven children of drinkers only ten, or 17.5 per cent., had normal constitutions and healthful growth. The ten sober families had sixty-one children, five only dying in the first weeks; four were affected with curable diseases of the nervous system; two only had inborn defects. The remaining fifty, 81.9 per cent., were normal in their constitutions and development.

In this statement we have a graphic object lesson of the evil effects of alcohol on the germ plasm. Natural selection had far more to do in removing those unfit to survive in the intemperate than in the temperate families.

A knowledge of the evil effects of alcohol on the unborn child was known to the ancients. The mother of Sampson was warned "not to drink any wine or strong drink nor to eat any unclean thing" because she was to conceive and bear a son who was to deliver Israel out of the hands of the Philistines. Manoah was so interested in what the angel of the Lord had said to his wife that he sought an interview with him for further confirmation, and asked: "How shall we order the child, and how shall we do unto him?" evidently meaning, "How shall we train and educate him?" and the same advice was given as before. Whatever view the reader may hold as to the inspiration or non-inspiration of the Bible, certainly this advice was good. Other examples similar to it are to be found, not only in the same book, but in numerous historical works, and also abundant evidence in our own time of the evil effects of alcoholic drinks on unborn children giving them a tendency to insanity, idiocy and other nervous diseases. A whole book might be written on this branch of our subject.

To what extent food affects the germ plasm we remain somewhat in ignorance. We know that it is from it that the body is nourished, and from it also the stored up or surplus matter in our systems is obtained. The larger the surplus the more highly will the offspring be endowed with energy is a fact clearly set forth by Mr. Spencer. A surplus of fatty food stored up in the body, however, cannot be of much service and may prove injurious. A deficiency of nitrogenous food would also, it seems to me, be an evil. The germ plasm, or its most important part, is a highly nitrogenous substance, like all protoplasm, or living matter. The highest form of germ plasm, that with a most complex molecular structure, would hardly be formed if there was a deficiency of nitrogenous matter in the blood.

Air is also food the same as bread is. The activities, the chemical changes in the body, are mainly, though not entirely, between the oxygen of the air and the carbon and hydrogen of our food. The body is quite as much injured by a deficiency of air inhaled into the lungs by exercise as by a deficiency of food, though the injury may be of a different nature. Physicians and others have long ago observed that the offspring of parents living much in the open air and sunlight are healthier and stronger than those of parents living in confined spaces, where air and light are deficient. Air which is impure, which is loaded with poisonous matter, if inhaled for a long time by the mother, lowers the standard of her health. In malarious regions, the vigor of the offspring is less, and the number who die in infancy greater, than in regions where the air and water are pure. Many years ago I remember reading in one of the journals devoted to sanitary science published in London, an account of a rural town where both air and water were of extraordinary purity, and in this town a very large percentage of the children born lived to grow to maturity. There is also an isolated region in France, bordering on the sea, where both air, water and climate are unusually salubrious, and though intermarriage has been practiced for a long time among the several thousand inhabitants, the people are remarkably well formed and healthy. Similar facts have been observed in other places. They indicate to us that a healthful climate, with good air and water, are important factors in all true stirpiculture.

While all diseases which exhaust the physiological resources of the system are detrimental to the offspring, there are certain ones which are peculiarly so. Specific diseases or those resulting from a sensual life are the first to be mentioned. If the bodies of either father or mother become saturated with the poison, which is probably a germ, then the child born of such parents will certainly be infected and either die at birth or live only a short and feeble life. It is one of the penalties of an impure life—a very severe one, no doubt, but perhaps not too severe, that the offspring of the sensualist must suffer the penalties for its parent's physiological sins. Medical men have long been trying to discover a remedy which will make it safe for a man infected with specific disease to marry and become a father, but so far they have not had much success. It is doubtful if they ever will.

Epilepsy is another disease which is so often transmitted to children that any one of either sex suffering from it had better abstain from parentage. If one parent is remarkably healthy, the children may escape the severest form of penalty; but even then they may suffer from nervousness and other diseases, and rarely enjoy robust health.

The question whether persons who have a consumptive tendency should become parents or not has frequently been discussed by sanitarians, but never settled. Such persons are frequently intellectual, and often of an unusually cheerful and hopeful disposition. They are, in most cases, quite prolific. In the female they generally make excellent wives and mothers; in the case of the male, they are not uncommonly good providers for their families, and also good fathers. Except in the worst cases, does the welfare of the race demand that they shall not marry and become parents. Probably not. But we must advise them to take the very best care of their imperfect bodies; to develop their chests by wise but not excessive physical training; to husband their physiological resources carefully; not to marry young, nor rear too many children. Excessive childbearing is a prolific cause in women of consumption, and excessive sexual indulgence is a frequent cause of it in both sexes.

These remarks should not be construed to mean that those who are already in the early stages of this disease, or whose families on both sides have been deeply affected by it, may become parents. They should not. But in the present state of society, we cannot hold men and women up to an ideal standard. Some slight risks may be taken, but not too great ones. As the race progresses in knowledge, however, we may raise our standards, and finally make them so high that no one with a tendency to any serious disease which is likely to affect the offspring unfavorably shall have any right to contribute to the world's population.

I have mentioned only a few of the many diseases which affect the germ plasm unfavorably. It is hardly necessary to extend the list.

One other subject deserves consideration, when I will bring this chapter to a close. Every child born into the world is, to a certain extent, an experiment. That is to say, the parents cannot predict its sex, nor what its chief characteristics will be. These depend on what potentialities are stored up in the germ plasm. If this be formed by parents in good health, with a surplus of vital force, and a long line of ancestors with normal lives, we may believe that if the environment be favorable, the child will develop so as to show the same characteristics, perhaps in an even higher degree. Whatever variations there are will not be much below or above the average line of its ancestors. The congenital characters will tend to be transmitted. They are in the germ plasm, even in great detail. Whether the acquired ones are transmitted may still be uncertain; but whether they are or not, normal right living will be sure to have good effects. Obey the laws of life and far better results will follow than if they are disobeyed.