"Certain observations on the embryology of the lower animals are held to afford direct proof of this theory of heredity, but they are too technical to be made clear to ordinary readers. A logical result of the theory is the impossibility of the transmission of acquired characters, since the molecular structure of the germ-plasm is already determined within the embryo; and Weismann holds that there are no facts which really prove that acquired characters can be inherited, although their inheritance has, by most writers, been considered so probable as hardly to stand in need of direct proof. "We have already seen in the earlier part of this chapter that many instances of change, imputed to the inheritance of acquired variations, are really cases of selection." And the rest of the remarks tend to convey the impression that Mr. Wallace adopts Professor Weismann's view, but, curiously enough, though I have gone through Mr. Wallace's book with a special view to this particular point, I have not been able to find him definitely committing himself either to the assertion that acquired modifications never are inherited, or that they sometimes are so. It is abundantly laid down that Mr. Darwin laid too much stress on use and disuse, and a residuary impression is left that Mr. Wallace is endorsing Professor Weismann's view, but I have found it impossible to collect anything that enables me to define his position confidently in this respect. This is natural enough, for Mr. Wallace has entitled his book "Darwinism," and a work denying that use and disuse produced any effect could not conceivably be called Darwinism. Mr. Herbert Spencer has recently collected many passages from "The Origin of Species" and from "Animals and Plants under Domestication," {26} which show how largely, after all, use and disuse entered into Mr. Darwin's system, and we know that in his later years he attached still more importance to them. It was out of the question, therefore, that Mr. Wallace should categorically deny that their effects were inheritable. On the other hand, the temptation to adopt Professor Weismann's view must have been overwhelming to one who had been already inclined to minimise the effects of use and disuse. On the whole, one does not see what Mr. Wallace could do, other than what he has done--unless, of course, he changed his title, or had been no longer Mr. Wallace.