Mainspring

“ This living filament from the father is also liable to have its propensities, or appetencies, altered at the time of its production by the imagination of the male parent; the extremities of the seminal glands imitating the motions of the organs of sense; and thus the sex of the embryon is produced; which may be thus made a male or a female by affecting the imagination of the father at the time of impregnation. ”

“ A system, in order to be true and natural, must agree with the sequence of the organs in the development of the embryo.” If the earlier manifested peculiarities are to be estimated more highly than those which afterwards make their appearance, then in those cases in which the structure of the adult animal requires one position in the system, and that of the larva another, the latter and not the former must decide the point. ”

“ In some animals the young have structures that attach them to the mother, as does the placenta of the mammals. In other cases the young develop membranes about themselves—like the amnion of the chick (fig. 7) and mammal—that would have shut off an adult animal from all intercourse with the outside {17}world. ”

“ The domesticated rabbit becomes tame from close confinement; the dog, intelligent from associating with man; the retriever is taught to fetch and carry; and these mental endowments and bodily powers are all inherited. Nothing in the whole circuit of physiology is more wonderful. How can the use or disuse of a particular limb or of the brain affect a small aggregate of reproductive cells, seated in a distant part of the body, in such a manner that the being developed from these cells inherits the characters of either one or both parents? ”

“ As the embryo unfolds, one by one these animal-actors come upon the stage, file past in phantom-like procession, throw off their drapery, and dissolve away into something else. Yet, as they vanish, each leaves behind a vital portion of itself, some original and characteristic memorial, something itself has made or won, that perhaps it alone could make or win,—a bone, a muscle, a ganglion, or a tooth,—to be the inheritance of the race. ”

“ I have remarked in the first chapter—but a long catalogue of facts which cannot be here given would be necessary to show the truth of the remark—that the reproductive system is eminently susceptible to changes in the conditions of life; and to this system being functionally disturbed in the parents, I chiefly attribute the varying or plastic condition of the offspring. The male and female sexual elements seem to be affected before that union takes place which is to form a new being. ”

“ Similarly the young mammal is developed within the body of the maternal organism to a point where it is able to perform the primitive functions of life. For weeks, months or even years, according to the class of the animal, it must be supported and protected by its parents. ”

“ Or as Sir Michael Foster put it, "The animal body is in reality a vehicle for ova or sperm; and after the life of the parent has become potentially renewed in the offspring, the body remains as a cast-off envelope whose future is but to die." ”

“ Many of these connections are inborn and seem to be as much a part of the heredity of the individual and the race as stature, the color of eyes and hair, or any other physical characteristic. Hence the nervous system is characterized by a multitude of more or less perfectly developed preorganized reactions which are a part of the individual's heredity. These preorganized reactions have been established through the operation of selection, biologists tell us, upon variations in the hereditary elements, in the same way in which the bodily characteristics of the species have been established. ”

“ Every man, and consequently all mankind, has accomplished his uninterrupted embryological development on his own account; no man and no human cell springs from the womb of an ape or any other animal, but only from the womb of a human mother, fertilised by a human father. ”

“ The somatic cells of the parent, therefore, as far as we know, contribute no living elements to the child; they merely provide temporary shelter and nutriment. The child, therefore, does not, as is popularly supposed, resemble his parent because his several parts are derived from similar parts of the parent—his head from his parent's head, his hands from his parent's hands, and so forth; he resembles him only because the germ-plasm which directed his development was a split-off portion of the germ-plasm which directed the development of the parent. ”

“ The formation of the organs of sexual generation, in contradistinction to that by lateral buds, in vegetables, and in some animals, as the polypus, the tænia, and the volvox, seems the chef d'œuvre, the master-piece of nature; as appears from many flying insects, as in moths and butterflies, who seem to undergo a general change of their forms solely for the purpose of sexual reproduction, and in all other animals this organ is not complete till the maturity of the creature. ”

“ A human body may have had some of the members removed but the physical life remains a unit. The embryo formed by the union of a masculine and a feminine cell will have a unit of physical life. During the nine months of gestation this unit of embryonic physical life will be incarnated in a unit of physical organism. Should a lobe of the brain of each parent, through which some mental or moral attribute functions, be removed, the child would inherit a unit of brain organism, for the reason that it inherited from the parents a unit of mental and moral life. ”

“ Before we can make any detailed analysis of the inheritance of characters we should have some general idea of the physical structure of animals and particularly some familiarity with the development of an individual from the egg, as well as some knowledge of the nature of the germ-cells.
The Cell the Unit of Structure.—If we examine one of the higher animals, as, for example, the horse, the dog, or man, we find that it is made up of a large number of constituents, such as bones, muscles, nervous elements, blood and other tissues. ”

“ I repeat, the reproduction of lost limbs is due to a process which is in all essential respects the same as that which originally produced them; the genesis of one group of cells is the necessary condition for the genesis of its successor, nor can this order be transposed. But—and the point is very important—it is not every part that can be reproduced, nor is it every animal that has reproductive powers. ”

“ Through the study of comparative anatomy, the fact has been discovered that the individuals composing the various orders of the great vertebrate series are all moulded “on the same general plan”; that up to a certain stage in the development of the several germs—for instance those of the man, the ape, the horse, the dog, etc.,—they are not distinguishable the one from the other, and that it is only at a later stage of development that they take on the peculiarities belonging to their own special kind. ”

“ Looking back, then, to the primal source of all nervous organization, in the remote animal in which the nervous structure and action were at the crudest state of development, and remembering that there was a power of transmitting it to offspring, and that natural and sexual selection were unceasingly operating to expand and perfect it, we may trace the successive stages of its modification and growth, from the lowest to the highest, until we reach in the primeval man the highest development that it had yet attained. ”

“ What I conceive to happen is somewhat as follows:—In animals which exhibit neither sexual dimorphism nor seasonal armature or ornamentation, the influence of the generative organs is exerted equally upon the sexes, as well as, probably, throughout life. In animals exhibiting the phenomenon either of sexual dimorphism or seasonal armature or ornamentation, the generative organs, when the individual is young, have usually little or no influence on the body, which follows in its growth the simplest possible laws. ”

“ In the fœtal type animals undergo the whole or nearly the whole of their development within the egg or within the body of the parent, and are hatched in a condition closely resembling the adult; and in the larval type they are born at an earlier stage of development, in a condition differing to a greater or less extent from the adult, and reach the adult state either by a series of small steps, or by a more or less considerable metamorphosis. ”

“ The child in the womb begins as a cell, and develops through the stages of evolution, becoming an embryo worm, fish, quadruped, ape, and, finally, a human baby.
The child is born with the bodily and mental qualities inherited from many generations of beasts and many generations of men. ”

“ In the simplest forms of conjugation the functions of both parents appear to be identical, but in organisms which are a little more specialized we find male and female reproductive bodies, and the offspring is the result of the union of the male element of one individual with the female element of another; that is, we have true sexual reproduction in its simplest form. ”

“ While such experiments must not be stretched too far, in application to the human species, they certainly offer striking evidence of the fact that the characters of any individual are mainly due to something in the germ-plasm, and that this germ-plasm is to a surprising degree independent of any outside influence, even such an intimate influence as that of the body of the mother in which it reaches maturity. ”

“ The science of embryology, then, is the science of individual development, and includes within its purview all those changes of form and structure, whether embryonic, larval or post-larval, which characterize the life of the individual. The beginning of this period is precise and definite—it is the completion of the fertilization of the ovum, in which the life of the individual has its start. ”

“ This law of the paramount importance of the growth of the central nervous system for all upward progress in the evolution of animals receives confirmation from the study of the development of individuals, especially in those cases where a large portion of the life of the animal is spent in a larval condition, and then, by a process of transformation, the larva changes into the adult form. ”

“ This is notably the case, for example, with the reproductive organs which, though developed during the life of the embryo, remain functionless until the period of adolescence. The development of the human mind and intellect too, although depending, of course, upon the embryonic growth of the brain and the nervous system generally, is a matter of time and the environment subsequent to birth. ”

“ When we examine the human embryo in the third or fourth week of its development, we find it to be quite different in shape and structure from the full-grown human being, but almost identical with that of the ape, the dog, the rabbit, and other mammals, at the same stage of ontogeny. ”

“ In the most highly developed families of the animal kingdom, these last come more and more into the foreground as independent soul-organs. In correspondence with the extraordinarily complicated structure of their central nervous system (the brain with its wonderful complex of ganglion-cells and nerve-fibres) , the many-sided activity of such animals attains a wonderful degree of development. ”

“ We have given protoplasm, a strange substance of marvellous capacities, which we call functions, and possessing a power of developing into beings of ever higher grades of organization. Environment proves to be a combination of forces working for the higher development of functions in a certain orderly sequence. And every lower function in the ascending line demands the development of the next higher. Digestion demands muscle, and muscle nerve, and nerve brain. We shall soon see that mammalian structure had to culminate in the family, and the family demands unselfishness and obedience. ”

“ In proportion as any particular faculty or propensity acquires paramount activity in any individual, these organs develope themselves, and their development becomes externally obvious by corresponding lumps and bumps, exuberances and protuberances, on the osseous compages of the occiput and sinciput. In all animals but man, the same organ is equally developed in every individual of the species: for instance, that of migration in the swallow, that of destruction in the tiger, that of architecture in the beaver, and that of parental affection in the bear. ”

“ These two things are universal because of the existence and characteristics of germ-cells. We may look at this a little closer.
Every species of animal, in the process of reproduction brings forth offspring similar to itself. This is expressed in the familiar proverb that “like produces like.” One does not expect grapes from thorns, nor is it possible to construct a silk purse out of a sow's ear. ”

“ It is a matter of common knowledge that living things repeat in a more or less blurred and abbreviated series their generalized pedigree in their embryological changes. For instance, as we shall presently remind the reader, the developing chick or rabbit passes through a fish like stage, and the human fœtus wears an undeniable tail. ”

“ From the transitory stages through which man passes in his development being more or less permanently retained in the lower animals, from his organization exhibiting in a rudimentary condition structures which are fully developed in the lower animals, from abnormal characters such as certain muscles appearing in man which are usually only present in monkeys, we concluded in our chapter on Embryology that man had descended from some animal form. ”