Page:Popular Science Monthly Volume 45.djvu/196

182 mother during the growth of the embryo. This may be true, but it is unimportant. The time required to develop the embryo is too short for the environment to produce any material change however strong the tendency might be at the time in the direction of such change. It is chiefly the uncombined sexual elements which are admitted by all to be undergoing specific transformation."

This is the main issue, and if admitted, the Neo-Lamarckian asks no more. How then does Weismann evade this issue? He says:

"It is self-evident from the theory of heredity here propounded, that only those characters are transmissible which have been controlled—i. e., produced—by determinants of the germ, and that consequently only those variations are hereditary which result from the modification of several or many determinants in the germ-plasm, and not those which have arisen subsequently in consequence of some influence exerted upon the cells of the body. In other words, it follows from this theory that somatogenic or acquired characters can not he transmitted."

From these and other statements we are obliged to infer that while he admits the power of external influences to affect the somatic cells at all points where they impinge, adapting the organs of the body to the environment, and also admits that inequalities of nutrition (which at bottom are the same thing) modify the germ cells, he denies that these two facts have any connection with each other. Obvious as it is that the species becomes modified to suit the changing environment just as does the individual, he attributes the former wholly to natural selection and the latter wholly to direct adaptation. All, therefore, that is gained by this latter process is necessarily lost, and we have a strong indictment against Nature, "who," he says, "always manages with economy." It seems far more logical to argue from the economy of Nature and the parallelism of these two processes for a causal connection between them.

But it must not be forgotten that he now makes natural selection itself entirely dependent upon "inequalities of nutrition" in the germ-plasm as its universal antecedent. Is this then so widely different from the direct adaptation that takes place in the somatic cells? Let us see how narrow the distinction grows with careful analysis. He admits that alcohol affects the germ and sperm cells by debilitating them and makes weakly children. He would admit the same of any deleterious drug. He would not deny that any disease that debilitates the parents