The influence exerted by Jacob"s rods was of a different character from that which is supposed to give rise to the marking of offspring before birth, which is not uncommon if we are to accept as true all the cases mentioned in books referring to the subject. What occurred took place _before_ conception, and not subsequent to it, as in these cases.
Nevertheless, both cla.s.ses of phenomena are recognized by so competent an authority as M. Th. Ribot, who, in his "Heredity,"[57:A] when criticising Dr. Lucas" explanation of the origin of the numerous exceptions to the law of heredity, as being due to the operation of the law of spontaneity, affirms that there is no law of spontaneity, but that all such exceptions may be explained by reference to certain causes of diversity. M. Ribot gives three causes of diversity, which are: 1--Antagonistic heredities of two parents; 2--Accidental causes in action at the moment of generation; 3--External and internal influences subsequent to conception. He a.s.signs but little importance to causes acting after birth, such as diet, climate, circ.u.mstances, education, physical and moral influences, because, though they may produce serious effects, these are not radical. Possibly, however, since the advance made in the education of those who are born with defects of the sensory apparatus, M. Ribot would somewhat modify his opinion on that point. As to the causes which operate at the period of conception, or subsequent thereto and before birth, he says, in relation to the latter cla.s.s, they "are all the physical and moral disturbances of uterine existence--all those influences which can act through the mother upon the fetus during the period of gestation; impressions, emotions, defective nutrition, effects of imagination." He adds: "These causes are very real, despite the objections of Lucas, who attacks them in order to establish his law of spontaneity. We see from examples that between considerable causes and their effects there exists an amazing disproportion."
The causes of diversity which operate at the instant of conception depend, says Ribot, "less upon the physical and moral natures of the parents than on the particular state in which they are at the moment of procreation." This fact is referred to by M. de Quatref.a.ges as fully proving the universality of the law of heredity, and M. Ribot adds, "It enables us to understand that those transitory states which exist at the moment of conception may exert a decisive influence on the nature of the being procreated, so that often, where now we see only spontaneity, a more perfect knowledge of the causes at work would show us heredity."
Professor E. D. Cope, the well-known author of "The Origin of the Fittest," would seem to doubt the truth of the stories of birthmarks on the ground that "the effect of temporary impressions on the mother is not strong enough to counterbalance the molecular structure established by impressions oftener repeated throughout much longer periods of time."[59:A] And yet there is no doubt that birthmarks do occasionally occur, although it is very difficult to obtain properly authenticated cases of them.
AN ILl.u.s.tRATIVE CASE.--How great is the influence on unborn offspring of the mother"s mental condition, as well as the effect over them of pleasant surroundings, is shown by the following case. A young girl attracted attention by her beauty and by the superiority of the type she exhibited over that of either of her parents, and on her mother being spoken to on the subject she remarked:
"In my early married life my husband and I learned how to live in holy relations, after G.o.d"s ordinance. My husband lovingly consented to let me live apart from him during the time I carried this little daughter under my heart, and also while I was nursing her. Those were the happiest days of my life. Every day before my child was born, I could have hugged myself with delight at the prospect of becoming a mother. My husband and I were never so tenderly, so harmoniously, or so happily related to each other, and I never loved him more deeply than during those blessed months. I was surrounded by all beautiful things, and one picture of a lovely face was especially in my thought. My daughter looks more like that picture than she does like either of us. From the time she was born she was like an exquisite rosebud--the flower of pure, sanctified, happy love. She never cried at night, was never fretful or nervous, but was all smiles and winning baby ways, filling our hearts and home with perpetual gladness. To this day, and she is now fourteen years old, I have never had the slightest difficulty in bringing her up.
She turns naturally to the right, and I never knew her to be cross or impatient or hard to manage. She has given me only comfort; and I realize from an experience of just the opposite nature that the reason of all this is because my little girl had her birthright."
The future experience of this lady was, however, of a very different nature. She added:
"A few years later I was again about to become a mother, but with what different feelings! My husband had become contaminated with the popular idea that even more and frequent relations were permissible during pregnancy. I was powerless against this wicked sophistry, and was obliged to yield to his constant desires. But how I suffered and cried; how wretched I was; how nervous and almost despairing! Worst of all, I felt my love and trusting faith turning to dread and repulsion.
"My little boy, on whom my husband set high hopes, was born after nine of the most unhappy, distressing months of my life, a sickly, nervous, fretting child--myself in miniature, and after five years of life that was predestined by all the circ.u.mstances to be just what it was, after giving us only anxiety and care, he died, leaving us sadder and wiser.
"I have demonstrated to my own abundant satisfaction that there is but one right, G.o.d-given way to beget and rear children, and I know that I am only one of many who can corroborate this testimony."
The following case of prenatal culture appeared in _The Philosophical_ for October 5, 1895, above the signature of "John Allyn," who says:
"About forty years ago I was a neighbor of a young couple who had been recently married. They were of fair natural abilities, but not highly educated. The wife could play on the piano well and accompany it with her voice. The husband was a house-building contractor. Before their first child was born the wife was provided with instruments for drawing, and interested herself in their use and mathematical calculations connected with them. The child proved to be a boy, who took to architectural drawing as by instinct. With very little effort he became proficient, and is now employed at a high salary by the Southern Pacific Railroad as their architect.
"Some years later, before the second child was born, the mother interested herself with music with reference to the effect it would have on the unborn child. This child proved to be a girl, who is now an expert singer, finding ready employment in opera companies. Though not a star, she has a superior talent for music which enabled her to take advantages of musical training easily."
BELIEFS OF PRIMITIVE PEOPLES.--Whenever such cases happen, it is under the influence of some very strong emotion, during the period of gestation, arising from the action on the nervous system of the mother by an external object presented to the sight, the organ of which would seem to have an intimate a.s.sociation with the general muscular system.
There is nothing to show that primitive peoples recognized the action of prenatal influence through the senses; but there is a very curious custom, which is so widespread at the present time that we may well suppose it to have been formerly almost universal, dependent upon the imagined effect of the eating of animal flesh. All primitive peoples believe that a man acquires physical or mental characteristics from animals of whose flesh he partakes. Cannibalism is closely connected with this notion, as the man who eats part of the body of a foe is thought to become endowed with the victim"s courage, strength or other special quality. Probably the Mosaic regulations as to unclean animals, that is, animals unfit for food, was based on such an idea; and certainly the command to abstain from eating blood was thus connected; as we are told the blood is the life, and if so, then it must be the carrier of vital influences.
The custom above referred to, which is known to ethnologists as _la couvade_, or "hatching," supposes injurious action on the organism of the child of food eaten by its parents, as appears from the facts brought together by Dr. E. B. Tylor in his "Researches into the Early History of Mankind." The couvade usually has reference to the period immediately following the birth of a child; but among the native tribes of South America, where it is more extensively prevalent than elsewhere, it is observed while the child is still unborn. Thus, in Brazil, according to Von Martius, "A strict regimen is preserved before the birth; the man and the woman refrain for a time from the flesh of certain animals, and live chiefly on fish and fruits." The peculiarity of the couvade custom, and that which gives it its special interest, is the fact that it usually concerns the father and not the mother, as injury to the child is supposed to be due to the conduct of the former rather than of the latter. Thus, among the Land Dyaks of Borneo, "The husband, before the birth of his child, may do no work with a sharp instrument, except what is necessary for the farm; nor may he fire guns, nor strike animals, nor do any violent work, lest bad influences should affect the child; and after it is born the father is kept in seclusion indoors for several days, and dieted on rice and salt, to prevent not his own but his child"s stomach from swelling."
Here food abstinence takes place after the birth of the child, but, according to Brett, in Guinea "Some of the Acawois and Caribi nations, when they have reason to expect an increase of their families consider themselves bound to abstain from certain kinds of meat, lest the expected child should, in some mysterious way, be injured by the partaking of it. The acouri (or agouti) is thus tabooed, lest, like that little animal, the child should be meager; the haimara, also, lest it should be blind--the outer coating of the eye of the fish suggesting film or cataract; the labba, lest the infant"s mouth should protrude like the labba"s, or lest it be spotted like the labba, which spots would ultimately become sores."
Another related case, of more recent observation, is that of the Motumotu of New Guinea, who say that after conception the _mother_ must not eat sweet potato or taro, lest the head of the child grow out of proportion, and the _father_ must not eat crocodile or several kinds of fish, lest the child"s legs grow out of proportion. At Suan, a husband shuts himself up for some days after the birth of his first child, and will eat nothing.[65:A]
Various explanations of the custom of couvade have been offered, and probably C. Staniland Wake is right when he states that it is connected with the idea that the father is the real source of the child"s life.[66:A] As he points out, on the authority of M. Girard-Teulon, among the European Basques, even at the present day, a husband enters his wife"s abode only "for the purpose of reproduction, and to work for the benefit of his wife." Mr. Wake remarks that, "With some of the Brazilian tribes, when a man becomes a father he goes to bed instead of his wife, and all the women of the village come to console him for the pain and suffering he has had in making this child." This agrees with the idea entertained by so many peoples that the child is derived from the father only, the mother being merely its nourisher. When such an idea is held, it is not surprising if, as among the Abipones, the belief is formed that "the father"s carelessness influences the new-born offspring, from a natural bond and sympathy of both," or if the father abstains, either before or after the child"s birth, from eating any food, or performing any actions which are thought capable of doing it harm. Still more so, if the child is regarded, as is sometimes the case, as the reincarnation of the father, a notion which is supported by the fact, pointed out by Mr. Gerald Ma.s.sey, that in the couvade the parent identifies himself with the infant child, into which he has been typically transformed.
That conclusion agrees with the opinion expressed by Mr. Tylor, that the couvade "implicitly denies that physical separation of "individuals"
which a civilized man would probably set down as a first principle common by nature to all mankind... . It shows us a number of distinct and distant tribes deliberately holding the opinion that the connection between father and child is not only, as we think, a mere relation of parentage, affection, duty, but that their very bodies are joined by a physical bond, so that what is done to the one acts directly upon the other."[67:A] The couvade custom is thus closely connected with the question of the special relationship of a child to one or other of its parents. Curious notions on this subject have been formed from time to time; but the ancients almost universally entertained the idea held by the Greeks that "the father, as endowed with creative power, was clothed with the divine character, but not the mother, who was only the bearer and nourisher of the child." Professor Hearn accepts this view in his work, "The Aryan Household," and suggests as the Aryan thought on the subject: "A male was the first founder of the house. His descendants have "the nature of the same blood" as he. They, in common, possess the same mysterious principle of life. The life spark, so to speak, has been once kindled, and its ident.i.ty, in all its transmissions, must be preserved. But the father is the life-giver. He alone transmits the life spark, which from his father he received. The daughter receives, indeed, the principle of life, but she cannot transmit it."
M. Ribot, who, as we have seen, endorses the popular belief as to the possibility of the fetus being affected, during uterine existence, through the organism of the mother, reduces all the obscure causes of deviation from heredity to two cla.s.ses. Of these, the first is the disproportion of effects to causes, already mentioned; and the second is the transformation of heredity. As to the first of these causes, he lays it down as a general truth that "the more complicated the mechanism, the greater the disproportion between accidental causes and their effects."
He supports this conclusion by reference to Geoffroy Saint-Hilaire"s researches on the production of monsters, and he affirms that the disproportion between cause and effect cannot be foreseen by measuring, but is known only by experience, as "psychological laws are a.n.a.logous now to mechanical and now to chemical laws," so that it is impossible to proceed by deduction from causes to effects. (Page 207.)
BIRTHMARKS RARE.--And yet the very fact that cases of birthmarks are comparatively rare, proves the greatly preponderating influence of heredity over the const.i.tution of the offspring, modified by the disposition of the parents at the time of procreation. Professor Cope has some explanatory remarks on that subject which deserve quotation. He says--after referring to the hypothesis that growth-force may be, through the motive force of the animal, directed to any locality, whether the commencement of an executive organ has begun or not--that "A difficulty in the way of this hypothesis is the frequently unyielding character of the structure of adult animals, and the difficulty of bringing sufficient pressure to bear on them without destroying life.
But, in fact, the modifications must, in most instances, take place during the period of growth. It is well known that the mental characteristics of the father are transmitted through the spermatozoid, and that, therefore, the molecular movements which produce the mechanism of such mental characters must exist in the spermatozoid. But the material of the spermatozoid is combined with that of the ovum, and the embryo is compounded of the animal contents of both bodies. In a wonderful way the embryo develops into a being which resembles one or both parents in minute details. This result is evidently determined by the molecular and dynamic character of the original reproductive cells which necessarily communicate their properties to the embryo which is produced by their subdivisions." Professor Cope goes on to say, "Richard Hering has identified this property of the original cells with the faculty of memory. This is a brilliant thought, and, under restriction, probably correct. The sensations of persons who have suffered amputation show that their sensorium maintained a picture or map of the body so far as regards the location of all its sensitive regions. This simulcrum is invested with consciousness whenever the proper stimulus is applied, and the character of the stimulus is fixed by it. This picture probably resides in many of the cells, both sensory and motor, and it probably does so in the few cells of simple and low forms of life. The spermatozoid is such a cell, and, how or why we know not, also contains such an arrangement of its contents, and contains and communicates such a type of force. It is probable that in the brain-cell this is the condition of memory of locality. If, now, an intense and long-continued pressure of stimulus produces an unconscious picture of some organ of the body in the mind, there is reason to suppose that the energies communicated to the embryo by the spermatozoid and ovum will partake of the memory thus created. The only reason why the oft-repeated stories of birthmarks are so often untrue, is because the effect of temporary impressions on the mother is not strong enough to counterbalance the molecular structure established by impressions often repeated throughout much larger periods of time."[71:A]
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 cla.s.s we see especially the action of direct adaptation; in the second, the results of the cessation of the action. A third cla.s.s 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 cla.s.s."[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 const.i.tutes 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 ma.s.s 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 const.i.tuent 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 a.n.a.logous 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 a.s.signs for the origin of such germ-variations are of three kinds. These are: 1--Union of s.e.xual nuclei which are not adapted for copulation; 2--Disturbance of the copulatory process itself; 3--Injurious influences which affect the s.e.xual nuclei or the fertilized ovum at a time when separation of the s.e.xual 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 const.i.tutional anomaly arises, which is not inherited, or only the s.e.xual 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 s.e.xual 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 s.e.xual 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 trans.m.u.tation)."
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, apt.i.tude for the exact sciences, energy of will, etc.;" the mania of progenitors may be changed in the descendants into "apt.i.tude 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 s.e.xual excesses, overwork, etc., may give rise to neuropathic const.i.tutions, 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 cla.s.sic. 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 a.n.a.logous 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, b.i.t.c.h, 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 a.s.serting his influence on a subsequent progeny, although this fact is one of comparatively rare occurrence."