| OCR Text |
Show ~82 DARWINIAN A. the conquerors. The saying that '11 house <.livided against itself cannot stand,' receives in Nature its flattest contradiction. Civil war is here the very instrument of progress; it brings u.bout the survival of the fittest. Original differences in the cell-colonies, however slight, will bring about differences of life and action; the latter, continued through successivu generation~, will wi<len the origin.al differences ~f structnr~; innumerable species will thus sprmg up, branchmg forth m every direction from the original stock; and the competition of these species among each other for the ground they occupy, or the food they seek; will bring out and develop the powers of the rivals. One chief cause of superiority will lie in tho division of labor instituted by each colony; or, in other words, in the localization of the colony's functions. In the primitive associations (as in the lowest organisms existing now), each cell performed much the same work as its neighbor, an.d the ft~nctions necessary to the existence of the whole (ahmentatwn, digestion, respir~tion, etc.) were exercised by every colonist in his own behalf. Social life, however, acting upon the cells as it acts upon the members of a human family, soon created .differences among them-differences ever deepened by contmnance and which by narrowing the limits of each colonist's activit~, and incre~sing his dependence on the rest, rendered him fitter for his special to.sk. Each function was thus gradually monopolized; but it came to be the appanage of a single group of cells, or o1·gan j and so excellent did this arrangement pro~e, so greatly were the powers of each commonwealth enhanced by the division of its labor, that the more organs a colony possessed, the more likely it was to succeed in its struggle for life .... We shall go no furtl1er, for :he reader wi:l easily fill out the remainder of the picture for himself. M:an 1s but an immenf;je colony of cells, in which the division of labor, together with the centralization of the nervous sys~em, l1~s reached its highest limit. It is ehiefly to this that Ins supenority is due; a superiority so great, as regards certain fu~ctio~s of the brain, that he may be excused for having demed his humbler relatives and dreamed that, standing alone in the cen-tre of the univers'e , sun, moon, :mel stars, were made for h'1 m. " EVOLUTIONARY TELEOLOGY. 383 Let us learn from the same writer how both eyes of the :flounder get, quite unintentionally, on the same side of the head. The writer makes much of this case (seep. 372), and we are not disposed to pass it by: ".A similar application may be made to the Pleuronecta. Presumably, these :fishes had adopted their peculiar mode of swimming long before the position of their eyes became adapted to it. .A spontaneous variation occmrred, consisting in the passage of one eye to the opposite side of the head; and this variation afforded its possessors such increased facilities of sight tlJat in the course of time the exception became the rule. But the remarkable-point is, that the law of heredity not only preserved the variation itself, but the date of its occurrence; und that, although for thousands of years the adult Pleuronecta have had both eyes on the same side, the young still continue during their earlier development to exhibit the contrary arrangement, just as if the variation still occurred spontaneously." Here a wonderful and one would say unaccountable transference takes place in a short ~ime. As Steenstrup showed, one eye a-ctually passes through the head while the young fish is growing. We ask how this comes about; and we are told, truly enough, that it takes place in each generation because it did so in the parents and in the whole line of ancestors. Why offspring should be like parent is more than any one can explain; but so it is, in a manner so nearly fixed and settled that we can count on it ; yet not from any absolute necessity that we know of, and, indeed, with sufficiently striking difference now and then to demonsti ·ate that it might have been otherwise, or is so in a notable degree. This transference of one eye through the head, from the side where it would be nearly useless to that in which it may help the other, ben,rs all |
