Page:Popular Science Monthly Volume 23.djvu/541

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PERRIER ON THE THEORY OF DESCENT.

inorganic to the organic. Secondly, he refused to account, by it alone, that is, by the combined action of the environment and of heredity, for living forms; but had recourse, to explain some among them, to an internal nisus, or an original preformation analogous to final causes. Lastly, he believed that the general laws of evolution expired in some way at the threshold of the human world, and that human consciousness is formed after other laws than the organic consensus. It was the part of philosophy, now in possession of an idea of science which it owes largely to the scientific men themselves, to indicate these later reserves. For it is, after all, no small matter to know what is of science and what is not. It is imperatively necessary for us to fix our eyes on this capital point, and to decide among ourselves whether those who in their researches accord a part to final causes, and attribute an exceptional position in nature to man, are performing a work of science or of metaphysics. This is why, without losing sight of the rare merits of the work we have named, we have thought it proper to point out the ambiguous character of some parts of it.

Now, M. Perrier has resolutely canceled most of his reserves. The second part of his preface, in which he for the first time traces the geographical distribution of the species of terrestrial lumbrici, and points out the consequences of such distribution both in respect to specific characteristics and from the geological point of view, is out of our province to consider. The first part, which is devoted to a general appreciation of Darwin's work, has a high philosophical significance; and we here give a summary of the whole of it.

"Until within the last twenty years," says the author, "living beings were nearly always studied independently of the medium in which they live and of the relations which they form with each other. Each of them appeared to be a distinct entity, owing nothing except to itself, capable of abstracting itself from every modifying action on the part of external agents, created once for all in view of certain conditions of existence, marvelously adapted to these conditions, but unable to extricate itself from them except at the cost of perishing, in perfect equilibrium with the supposed unchangeable medium, but destined to disappear whenever the equilibrium was broken. This false conception of the living being has caused the failure of every essay at a philosophy of the natural sciences which has been attempted till now."

M. Perrier then shows by a small number of selected examples that each being, under the pressure of variable circumstances is, aside from any preconceived plan, adapted to its environment, even when it may not have seemed primarily destined to live in it; some fishes to a life in the air, some mammals and some birds to an aquatic life. He remarks that the living beings of the environment are the preponderant part of the medium for each species. Adaptations not less close than those which unite organisms to the physical medium, put organisms in