Model (reproduction)

“ But however they may have arisen, what especially interests us at present is, to remark that, once in existence, varieties obey the fundamental law of reproduction that like tends to produce like; and their offspring exemplify it by tending to exhibit the same deviation from the parental stock as themselves. ”

“ Reproduction a group—not an individual problem. Conflict between specialization and adaptation. Intelligence makes for economy in adjustment to environment. Reproduction, not production, the chief factor in the sex problem. ”

“ A partial transformation of the male structure makes the female. A suitable adjustment of the male organs, and the implanting of the sexual impulse in both sexes, by the agency of the gods, make provision for generative reproduction, and a species is formed, which takes the place of the primitive non-sexual type which did not reproduce itself in the original scheme. ”

“ We have observed that, according to naturalists, the earliest forms of life which appeared on the earth were androgynous or hermaphrodite, that the two elements necessary for reproduction were originally confined within one and the same individual within which were carried on all the functions of reproduction. Later, however, a division of labour arose, and these two original functions became detached, after which time the reproductive processes were carried on only through the commingling of elements prepared by, or developed within, two separate and distinct individuals. ”

“ Surely if a machine is able to reproduce another machine systematically, we may say that it has a reproductive system. What is a reproductive system, if it be not a system for reproduction? And how few of the machines are there which have not been produced systematically by other machines? But it is man that makes them do so. Yes; but is it not insects that make many of the plants reproductive, and would not whole families of plants die out if their fertilisation was not effected by a class of agents utterly foreign to themselves? ”

“ There came a time in the evolution of the groups possessing sexual reproduction, when increasing specialization necessitated the division into reproductive and non-reproductive cells. When a simple cell reproduces by dividing into two similar parts, each developing into a new individual like the parent, this parent no longer exists as a cell, but the material which composed it still exists in the new ones. ”

“ We shall therefore pass on to this mode of reproduction. It is well known that, in all higher animals, just as in Man, an individual cannot reproduce by itself; the co-operation of two individuals is necessary, and these—the male and the female—differ essentially from each other in many particulars. ”

“ It was by chance that human observation brought the latter fact to light first, and therefore led us for so long to accept the idea that fertilization, that is, amphimixis, and development, that is, reproduction, are one and the same ”

“ The offspring will thus be the result of the unfolding of a bit of germ plasm which will be different from that from which either of its parents developed, and these differences will result in congenital variations. Sexual reproduction thus results in congenital variations; and if congenital variations are necessary for the evolution of the living machine—and we shall soon see reason for believing that they are—we find that sexual reproduction is a device adopted for bringing out such congenital variations. ”

“ By considering, under this point of view, generation by sexes, we should conclude it to be the most general mode of reproduction, as it is in fact. Beings, whose organization is the most complete, as animals, whose bodies compose a whole, which can neither be separated nor divided, and whose powers are con-centered to one single point, can only reproduce by this mode; because they contain only particles which resemble each other, and whose union can only be made by different particles, furnished by another individual. ”

“ We are assured that the principles of construction and destruction are mutually employed in the reproductive processes, that continuous death means continuous life,—the katabolic or disruptive tendencies of the male being necessary to the anabolic or constructive habits of the female. As it is in reproduction, so has it been through the entire course of development. ”

“ Now in this fissiparous mode of multiplication, which "is amazingly productive, and indeed surpasses in fertility any other with which we are acquainted," [11] we see most clearly the antagonism between individuation and reproduction. We see that the reproductive process involves destruction of the individual ”

“ How should we have imagined the possibility of fertilization for successive generations, of hermaphroditism, or of reproduction by fissure, etc., being found among the methods which Nature adopts for replenishing the earth, had we contented ourselves with an examination of the comparatively simple methods of ordinary sexual reproduction? ”

“ Having once originated, the sexual type of reproduction possessed a definite survival value which assured its continuation. Sex makes possible a crossing of strains, which evidently possesses some great advantage, since the few simple forms which have no such division of reproductive functions have undergone no great development and all the higher, more complicated animals are sexual. ”

“ In several of the cultivated plants named, the reproductive organs have themselves degenerated, either only the male, or only the female, or both at the same time; and some observers, accepting the hypothesis of an inheritance of functional modifications, have regarded this as the direct result of disuse during the long period of asexual reproduction. ”

“ Biologists have proceeded from this popular standpoint and regularly speak of 'mother cells,' and 'daughter cells.' It, therefore, does no violence to language or to science to say that life begins with the female organism and is carried on a long distance by means of females alone. In all the different forms of a-sexual reproduction, from fission to parthenogenesis, the female may in this sense be said to exist alone and perform all the functions of life, including reproduction. ”

“ All things having life, increase and multiply upon an analogous principle, but the method of effecting that increase differs very considerably. In the human race, nature has furnished the sexes parts, which it is necessary for the purpose of reproduction, should approximate and commingle their elements or rudiments of future existence, and that, that intermixture should take place in the womb of the female. In some of the lower order of animals and in the vegetable world the sexes are combined in one object which object possesses the power of increase. ”

“ Biologists tell us that the meaning or purpose of sexual reproduction is to bring about greater organic variation. Now variation, as we have seen, is the raw material upon which natural selection acts to create the higher types. The immense superiority of sexual reproduction over asexual reproduction is due to the fact that it multiplies so greatly the elements of heredity in each new organism, for under sexual reproduction every new organism has two parents, four grandparents, and so on, each of which perhaps contributes something to its heredity. ”

“ When we pass from the implacental to the placental mammals we arrive at the crowning distinction between the two great systems of reproduction which separates them by a line that seems to forbid the idea that the one has grown out of the other by such causes as natural selection, and without a special and intentional creation of a new and different mode of operation. ”

“ 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. ”

“ Here, at last, Nature discloses a heretofore hidden aim, namely, the production of quality rather than quantity; and once she has started on this new path, she has pursued it with even greater eagerness than that of reproduction pure and simple. And here we pause to note a principle laid down by the students of Evolution, viz., that advancing evolution is accompanied by declining fertility. ”

“ In the earliest times, therefore, before sex was yet declared, we may imagine that physical environment was the great and only factor of change. Sexual reproduction introduces the new element of variation of offspring from which Nature makes her selections; and this element of variation is apparently the result of the union of diverse individuals, and the funding of these differences in a common offspring, and thus a double inheritance of individual characteristics from the parents and a multiple inheritance of the same from the ancestry. ”

“ Among men, Birth Control has now evolved from the unconscious and instinctive phase, and is now unfolding and manifesting on the plane of conscious and voluntary activity. The influence of deliberate intention and conscious design is now one of the important factors in the process. Here at this point we reach a totally new aspect of reproduction. In the past stages of evolution the original impetus toward reproduction has been checked and directed by Nature, working along instinctive and unconscious lines ”

“ These various facts ought to be well considered by any one who wishes to embrace under a single point of view the various modes of reproduction by gemmation, division, and sexual union, the reparation of lost parts, variation, inheritance, reversion, and other such phenomena. ”

“ II. That sex is determined in the moment of fertilization by the reciprocal interaction of male and female, of zoösperm and ovum. One variant of this theory maintains that each reproductive element strives for the reproduction of its own sex; that a struggle takes place and that the victor in the contest stamps its own sex-likeness upon the fertilized product. ”

“ Nature making no mistake, never putting on a fresh kind of leg, or head, or tail, but always tending to repeat and to return to the primitive type.
It is the same in sexual reproduction: it is a matter of perfectly common experience, that the tendency on the part of the offspring always is, speaking broadly, to reproduce the form of the parents. ”

“ The result is that, though reproduction is greatly slackened, evolution is greatly accelerated. The significance of sex, as Coulter puts it, "lies in the fact that it makes organic evolution more rapid and far more varied." It is scarcely necessary to emphasise that a highly important, and, indeed, essential aspect of this greater individuation is a higher survival value. ”

“ Individuals are here produced which alone acquire the power of sexual reproduction, and metagenesis is thus brought about, these individuals detaching themselves from the stock on which they originated, while the rest of the individuals remain in combination, and retain the asexual mode of propagation. ”

“ Yet the whole process of sexual reproduction undoubtedly has, as its origin and explanation, the fusion in the first cell of the new generation from which all the rest will arise, of the material of two distinct individuals. ”

“ But the case is very different with sexual reproduction. When once individual differences have begun to appear in a species propagated by this process, uniformity among its individuals can never again be reached. So far from this being the case, the differences must even be increased in the course of generations, not indeed in intensity, but in number, for new combinations of the individual characters will continually arise. ”

“ In conclusion, I should wish to call attention to an idea which is rather implied than expressed in this essay:—it is, that reproduction did not first make its appearance coincidently with death. Reproduction is in truth an essential attribute of living matter, just as is the growth which gives rise to it. It is as impossible to imagine life enduring without reproduction as it would be to conceive life lasting without the capacity for absorption of food and without the power of metabolism. ”

“ It may be inferred, therefore, that the higher animal types could not have been evolved without sexual reproduction, and something of the meaning or significance of sex in the whole life process will, therefore, be helpful in understanding all of the higher forms of evolution. ”

“ And thus this process continues, one variation after another being added, until the machine is slowly built into a more and more complicated structure, always active but with a constantly increasing efficiency. The construction is a natural one. A mixing of germ plasm in sexual reproduction or some other agencies produce congenital variations; natural selection acting upon the numerous progeny selects the best of the new variations, and heredity preserves and hands them down to posterity. ”

“ As long as Man has lived he has regarded this process of procreation as the essential factor in the origin of new individuals, and as he had no insight into the essence of the process he had necessarily to regard reproduction as something entirely mysterious, and the co-operation of the two sexes as a conditio sine qua non of reproduction in general ”