Page:Popular Science Monthly Volume 8.djvu/742

722 new generations by fission, and abdicate their individuality in favor of a greater or less number of new individualities. It is also to be seen in those organisms on whose surface a new organism is formed by the process of budding. Here the disintegration is perfect, or nearly so, but in the higher organisms the disintegration affects only an insignificant portion of the parent.

Why this special disintegration? Biology can give no answer, unless we suppose that the genesis of individuals belongs as a genus to a class of facts including all the phenomena of general disintegration which attend growth, and which mark the gradual decline of the organism. This supposition finds its warrant in the fact that, as a general rule, reproduction does not take place until growth and structural development approach their term, when the molecular forces of the physiological units find themselves in equilibrium with the forces of the organism as a whole, and with the forces from without. Disintegration would now set in, or, to speak more exactly, disintegration would now begin to show an excess over integration, for, ever since the earliest vital phenomenon, disintegration has constantly accompanied integration. Among the various modes in which the decline of the organism is gradually brought about, there is one which resembles all the others, inasmuch as it constitutes a loss to the individual, but which differs from them in that it gives rise to new organisms. In a large number of cases among individuals of the lower orders of organisms, units combined in a certain group, and carrying away with them, as we have seen, their own proper tendency to find the equilibrium of their forces in arrangements similar to those in which they were originally integrated, become detached, and form the centre of a new integration. But in a very large number of organisms, and in all higher organisms of both the organic kingdoms, reproduction takes place by the mixture of two products, the one germinal, the other spermatic, coming from slightly different physiological units. In virtue of a property found in the simplest organic elements, and still more markedly present in the complex organic elements of living things, the mixture of substances which differ little from one another gives rise to products that are less stable than their constituent elements. Accordingly, the result of this mixture, namely, the fecundated germ, is farther from the state of equilibrium than were the units emitted by each of the parents, in the shape of germinal and spermatic cells. The faint tendency which existed in each of these groups to produce evolutional phenomena is intensified with the instability of the mixture. From this we may infer, if not the impossibility, at least the difficulty of an agamic genesis, and the necessity of a genesis by concurrence of different sexes. This conclusion, derived from the law of equilibrium, which itself flows from the law of persistence of force, seems to be hardly in agreement with facts, since unquestionably there exists such a thing as agamic