Part 5

WHY CHILDREN RESEMBLE PARENTS.--That children reproduce the general and physical and mental characteristics of their parents in combination is unquestionable truth, although the particular mode in which they are communicated is yet undetermined, notwithstanding the fact mentioned by Professor Cope that they are somehow conveyed by the microscopic sperm and germ in the union of which the new being has its beginning. Thus every individual must possess the general characteristics of the primitive human family from which through a vast number of ancestors he has descended. And yet at every stage of descent the organism may have obtained fresh characters, or at least have undergone some modification. As remarked by Dr. G. H. Th. Eimer, "Every character which must have been formed through the activity of the organism is an acquired character. All characters, therefore, which have been developed by exertion are acquired, and these characters are inherited from generation to generation. The same holds for all organs atrophied through disease--the degree of atrophy is acquired and inherited. In the first class we see especially the action of direct adaptation; in the second, the results of the cessation of the action. A third class of acquired characters is to be traced simply to the immediate action of the environment on the organism, and, originally, at the commencement of their appearance, all characters must have belonged to this class."[72:A] We have here a general argument in opposition to the theory propounded by Professor Weismann, that acquired characters are not transmissible. Elsewhere (page 382) Dr. Eimer observes: "Phyletic growth, or the evolution of the organic world ever into higher and more complex forms, or at least into forms of different structure, is, as I have said, merely the sum of the processes of growth of the ancestors--together with the result of external influences on the forms during their development and their existence. This additional modification which the individuals as such undergo is--together with the influence of crossing--the very cause of the constantly progressing evolution. All that the members of a series of individuals directly connected by descent acquire constitutes together the material for the formation of a new species."

LIFE'S EXPERIENCES AFFECTING CHILD.--Unless characteristics acquired by an individual, that is, the modifications of the organism due to his own life experiences, are capable of being handed down to his offspring, it is difficult to see how any progress could be made in the development of the race. Weismann's declaration that acquired characters are not transmissible was a surprise to the scientific world when first made, but it has been accepted by many Darwinians. His conclusion is dependent on his doctrine of heredity, which differs from that propounded by Darwin, but is by no means new; as its leading ideas, as pointed out by Professor G. J. Romanes,[73:A] are largely a reproduction of those of Mr. Francis Galton, whose work on heredity attracted much attention when first published. The views of Darwin, Galton and Weismann on that subject have been compared by Professor Romanes, who explains the distinction between them. He says (page 133), after referring to the supposed continuity of the germ-plasm, common to the theories of Galton and Weismann, but not required by that of Darwin, "The three theories may be ranked thus--The particulate elements of heredity all proceed centripetally from somatic-cells to germ-cells (gemmules): the inheritance of acquired characters is therefore habitual.

"These particulate elements proceed for the most part, though not exclusively, from germ-cells to somatic-cells (stirp): the inheritance of acquired characters is therefore but occasional.

"The elements in question proceed exclusively in the centrifugal direction last mentioned (germ-plasm): the inheritance of acquired characters is therefore impossible."

The first of these theories is that of Darwin, and the last that of Weismann, whose notion of the continuity of germ-plasm supposes that no part of an organism generates any of the formative material which goes to make up its offspring. This material is regarded in much the same light as the sperm which the male parent confides to the keeping of the female, according to the notion of the ancient world above referred to. For, as Romanes states (page 26): "In each generation a small portion of this substance [germ-plasm] is told off to develop a new body to lodge and nourish the ever-growing and never-dying germ-plasm--this new body, therefore, resembling its so-called parent body simply because it has been developed from one and the same mass of formative material; and, lastly, that this formative material, or germ-plasm, has been continuous through all generations of successively perishing bodies, which therefore stand to it in much the same relation as annual shoots to a perennial stem: the shoots resemble one another simply because they are all grown from one and the same stock."

Although Professor Weismann denies that acquired characters, that is, individual peculiarities arising as the result of personal experience, are transmitted, he admits that congenital characters, that is, peculiarities with which an individual is born, are transmitted to offspring. As congenital characters must, originally, have been individual, it is not easy at first sight to perceive Weismann's real meaning. It is necessary, therefore, to enter more particularly into a consideration of his theory, which he regards as in general accord with Darwin's theory of pangenesis. Darwin supposes that all the cells of the body continually give off great numbers of _gemmules_, which are conveyed by the blood and deposited in the germ-cells of the organism. These cells are thus endowed with the power of developing a new organism of the same kind, each gemmule reproducing the cell from which it was derived. These ultimate vital units are called by Weismann _biophors_, but he supposes them not to be the ultimate "bearers of vitality." They are said to be arranged in groups to which the term _determinants_ is applied, and these groups are combined so as to form ancestral _ids_ or germ-plasms. Each determinant, which is made up of perfectly definite numbers and combinations of biophors, is the primary constituent of a particular cell, or of a group of cells, such as a blood corpuscle. The determinants thus "control the cell by breaking up into biophors, which migrate into the cell body through the nuclear membrane, multiply there, arrange themselves according to the forces within them, and determine the histological structure of the cell," impressing upon it its inherited specific character. The structure of the cell, and of every subsequent stage, exists therefore potentially in the inherited structure of the id, and the determination of its character "depends on the biophors which the corresponding determinant contains, and which it transmits to the cell."

GERM-PLASM.--While Weismann regarded germ-plasm as absolutely stable, the only mode by which congenital variation could be brought about was that of _amphimixis_, or intermingling of individuals in the process of generation. As modified, however, by his latest work, "The Germ-plasm, a Theory of Heredity," published in 1892, his theory now allows the plasm to be capable of modification, and he ascribes that variation to the direct effects of external influences on the biophors and determinants of the germ-plasm. The instability of this substance is so slight, however, that congenital variations cannot be acted on and perpetuated by natural selection, and the influence of amphimixis is thus required for the purpose. Mr. Herbert Spencer, however, in criticising Weismann's theory, declares that "functionally produced modifications of structure are transmissible," and he refers in support of his contention to the remarkable effect of arrested nutrition on the structure and habits of wasps and bees. It especially affects the reproductive organs, and hence there is no occasion to call in the aid of amphimixis to perpetuate the variations produced, its office being the blending of the elements on which the characteristics of offspring depend.

If it be asked how modifications are actually transmitted, we may say that it can be only by an affection of the germ-cell. This probably takes place by deviations in the structure of what Weismann calls determinants, or of groups of determinants, through rearrangement of their primary units. The modification would be preceded, however, by a corresponding change in the nerve centers concerned in the use or disuse of the organs affected. Mr. Spencer shows that under certain conditions changes take place in the conduct of certain insects, and that "the maternal activities and instincts undergo analogous changes,"[77:A] facts which point to a loss of nervous energy and to an intimate connection between the nervous system and the reproductive function. Use or disuse first increases or diminishes the activity of certain nerve centers, and this leads to a modification of the corresponding germ-cells. If so, the determinants, instead of being first affected, as proposed by Weismann, and thus determining the variations, are in reality modified as the result of the functional changes, and are thus capable of transmitting these changes to succeeding generations.

In a subsequent article, published in _The Contemporary Review_ for October, 1894, Mr. Spencer recapitulates his argument in favor of the transmission of acquired characters, and refers to observations made by Professor Hertwig and others, which he regards as "showing, firstly, that all the multiplying cells of the developing embryo are alike; and, secondly, that the soma-cells of the adult severally retain, in a latent form, all the powers of the original embryo-cell," facts which he rightly considers disproves Weismann's hypothesis of _panmixia_. If this is surrendered, then, says Mr. Spencer, "all that evidence collected by Mr. Darwin and others, regarded by them as proof of the inheritance of acquired characters, which was cavalierly set aside on the strength of this alleged process of panmixia is reinstated. And this reinstated evidence, joined with much evidence since furnished, suffices to establish the repudiated interpretation."

Great stress was laid by Professor Weismann, as evidence in support of his theory, on the supposed fact that the inheritance of injuries sustained during life has not been proved. Particular attention has been paid to this point by Dr. Eimer, in relation to which he remarks: "That injuries incurred during life are but seldom transmitted to the offspring does not appear to me wonderful: the inheritance of the complete form and complete activities of the organism, which took root such enormously long periods of time ago, and has been strengthened at each generation, will, as a rule, counterbalance in the offspring any such injuries incurred only once and not repeated."[79:A] This is the same argument as was used, as quoted above, by Professor Cope, to disprove the occurrence of birthmarks, and Dr. Eimer goes on to state that there are injuries which are not transmitted to offspring, although they are constantly repeated, as an instance of which he refers to the rupture of the hymen. He adds, however: "In such cases we must presume a specially effective power of correlative activity, directed to the part affected and residing in the whole organism--the same compensating power which leads in lower animals, during the life of the individual, to the regeneration of parts which have been lost or artificially removed. But these cases do not prove the general proposition that injuries are not inherited; they do not prove that even injuries which have been repeated during a considerable period are not inherited. Hitherto little importance has been attached to the demonstration of the inheritance of injuries. Yet single cases of the inheritance of injuries only once incurred seem to me to be thoroughly authentic."

CONGENITAL DEFORMITIES.--Professor Weismann, in replying to the criticisms of Professor Virchow, admitted the existence of a number of congenital deformities, birthmarks and other individual peculiarities, which are inherited, but he affirms that we do not know from what causes they first appeared, and that a great proportion of them proceed from the germ itself, and are due, therefore, to alteration of the germinal substance. There is no proof of this, however, according to Dr. Eimer,[80:A] who appeals to various facts in support of his contention that injuries and diseases are inherited. He thinks the degeneration of the tail in the higher mammals is a case in point, although it has required great periods of time to complete. Among other instances of inherited injuries mentioned by Dr. Eimer is one in which a scar over the left ear and temple, caused to a girl by being thrown from a carriage, was transmitted to her son and grandson, the son of the latter also showing absence of hair on the injured spot, although the defect gradually disappeared with him, nearly a hundred years after the accident. The case of Dr. Nosseler, who inherited from his mother a crushed finger joint, caused by an accident which happened two years before his birth, would seem to be conclusive proof that injuries are transmissible. Dr. Eimer refers also to the breeding of short-tailed pointers from dogs whose tails had been artificially shortened; and also to Brown-Sequard's experiments with guinea pigs, in which epilepsy was inherited by their offspring, who showed also the loss of certain phalanges, or even whole toes of the hind feet, the parents having suffered a similar loss owing to the division of the sciatic nerve. He adds that numerous other instances of the inheritance of injuries have been recorded, as "inheritance of the artificially shortened tail of the bull, of artificially produced hornlessness in cattle, many cases of inheritance in man of curvature in a finger, caused by injury, inheritance of the absence of one eye which had been lost by the father during life or by disease, etc."

The question of the inheritance of deformities and diseases, and the causes of the germ-variations on which it depends, have been considered by Zeigler, whose conclusions, as quoted by Dr. Eimer (page 186), are too important to be omitted. The causes which Zeigler assigns for the origin of such germ-variations are of three kinds. These are: 1--Union of sexual nuclei which are not adapted for copulation; 2--Disturbance of the copulatory process itself; 3--Injurious influences which affect the sexual nuclei or the fertilized ovum at a time when separation of the sexual cells from the body cells has not yet occurred. "If the embryo is injuriously affected at a later period," says Zeigler, "either a malformation or a constitutional anomaly arises, which is not inherited, or only the sexual cells are injured, in which case the body-cells develop normally, and a disturbance shows itself only in the development of the next generation." The union of sexual nuclei not adapted for copulation appears, however, to be "the most frequent and most important cause of hereditary local malformations as well as of hereditary morbid tendencies, or of a defect in any system of the whole organism." If the nuclei are altogether unadapted to each other, sterility occurs, as in the sexual nuclei of distinct species.

PSYCHICAL DISEASES.--Zeigler's conclusions are supported by reference to the enquiries of the distinguished psychiatrist, D. Von Krafft-Ebings, who has considered the heredity of psychical diseases, and in connection therewith mentions three "essential facts" which it is necessary to keep in view when dealing with that subject. The first of these facts is Atavism, by which "the bodily and mental organization and character can be transmitted from the first to the third generation, without any necessity that the second and intermediate one should exhibit the peculiarities of the first--thus the condition of the life and health of the grandparents are of interest for us." Secondly, "Only in rare cases is the actual disease transmitted in procreation (congenital insanity, hereditary syphilis), as a rule only the disposition thereto. Actual disease only occurs when accessory injurious influences produce an effect based upon that disposition. . . . We must, therefore, consider also the state of health of the relatives (uncles, cousins, aunts), and since here also the law of atavism holds good, the possible diseases of great-uncles and great-aunts." Thirdly, Dr. Von Krafft-Ebings says, "Only exceptionally does the same disease develop in ascendant as in descendant lines, in consequence of the transmission of morbid dispositions. On the contrary, there exists a remarkable variability in the forms of disease which may almost claim the value of a law (the law of polymorphism or transmutation)."

This law is referred to by M. Ribot as one of the causes of deviation from heredity, and he speaks of it as "transformation." As examples of transformation of heredity, Ribot refers to fixed ideas in the progenitor, which may become in the descendants "melancholy, taste for meditation, aptitude for the exact sciences, energy of will, etc.;" the mania of progenitors may be changed in the descendants into "aptitude for the arts, liveliness of imagination, quickness of mind, inconsistency in desires, sudden and variable will." "Just as real insanity," says Moreau of Tours, "may be hereditarily reproduced only under the form of eccentricity, may be transmitted from progenitors to descendants only in modified form, and in more or less mitigated character, so a state of simple eccentricity in the parent--a state which is no more than a peculiarity or a strangeness of character--may in the children be the origin of true insanity. Thus in transformations of heredity we sometimes have the germ attaining its maximum intensity; and again, a maximum of activity may revert to the minimum."[84:A]

It should be borne in mind, as mentioned by Von Krafft-Ebings,[84:B] that everything which debilitates the nervous system and the generative powers of the parents, "be it immaturity or too advanced old age, previous debilitating diseases (typhus, syphilis), mercurial treatment, alcoholic and sexual excesses, overwork, etc., may give rise to neuropathic constitutions, and thereby indirectly to every possible nervous disease in the descendants."

TELEGONY.--There is one remarkable phenomenon, spoken of by various writers as _telegony_, which has an important bearing on the subject of the transmission of acquired characters, and shows the action of prenatal influence in an unexpected form. It is referred to by Professor Romanes, when he says, "It has not unfrequently been observed, at any rate in mammals, that when a female has borne progeny to a male of one variety, and subsequently bears progeny to a male of another variety, the younger progeny presents a more or less unmistakable resemblance to the father of the older one."[85:A] This curious fact was considered, in relation to plants especially, by Darwin, who affirms, as quoted by Romanes, that it is of the highest theoretical importance, as "The male element not only affects, in accordance with its proper function, the germ, but at the same time various parts of the mother-plant, in the same manner as it affects the same parts in the seminal offspring from the same two parents. We thus learn that an ovule is not indispensable for the reception of the influence of the male element."

The curious phenomenon of telegony is not limited, however, to plants. Mr. Herbert Spencer drew attention, in _The Contemporary Review_ for March, 1893, to a case which has long been known to horsebreeders, and which may be said to have become classic. The facts were brought, by the Earl of Morton, to the attention of the Royal Society of Great Britain, as long ago as the year 1820. The Earl, who possessed a male quagga, said, in a letter to the President: "I tried to breed from the male quagga and a young chestnut mare of seven-eighths Arabian blood, and which had never been bred from; the result was the production of a female hybrid, now five years old, and bearing, both in her form and in her colour, very decided indications of her mixed origin. I subsequently parted with the seven-eighths Arabian mare to Sir Gore Ouseley, who has bred from her by a very fine black Arabian horse. I yesterday morning examined the produce, namely, a two-year-old filly and a one-year-old colt. They have the character of the Arabian breed as decidedly as can be expected, where fifteen-sixteenths of the blood are Arabian; and they are fine specimens of that breed; but both in their colour and in the hair of their manes they have a striking resemblance to the quagga. Their colour is bay, marked more or less like the quagga in a darker tint. Both are distinguished by the dark line along the ridge of the back, the dark stripes across the forehead, and the dark bars across the back part of the legs." Mr. Spencer refers to an analogous case of the influence of a wild boar over the subsequent progeny of a domestic sow, and it now appears that such effects are not so uncommon as the scientific world has supposed.

Professor Romanes made particular enquiries on this subject of professional and amateur breeders of animals, and he says most of his correspondents "are quite persuaded that it is of frequent occurrence, many of them regard it as a general rule, while some of them go so far as to make a point of always putting a mare, bitch, etc., to a good pedigree male in her first season, so that her subsequent progenies may be benefited by his influence, even though they be engendered by inferior sires."[87:A] His own more modest conclusion is that the evidence he obtained "is enough to prove the fact of a previous sire asserting his influence on a subsequent progeny, although this fact is one of comparatively rare occurrence."