THE EVOLUTION OF LIFE 



already dealt with these in the sixth chapter (as well as 

 in the ninth chapter of the History of Creation), I may 

 refer the reader thereto. None of these or similar at- 

 tempts has completely solved the very difficult problems 

 in question, and none of them has been generally re- 

 ceived. There is, however, one of them that we must 

 consider more closely, because it is not only regarded 

 by many biologists as the greatest advance of the theory 

 of selection since Darwin, but it also touches the roots 

 of several of the chief problems of biogeny. I mean the 

 much-discussed germ-plasm theory of August Weis- 

 mann (of Freiburg) , one of our most distinguished zoolo- 

 gists. He has not only promoted the theory of de- 

 scent by his many writings during the last thirty years, 

 but has also piit in its proper light the great importance 

 and entire accuracy of the theory of selection. But, in 

 his efforts to provide a molecular-physiological basis for 

 it, he has proceeded by way of metaphysical speculation 

 to frame a quite untenable theory of the plasm. While 

 fully recognizing the ability and consistency and the 

 able treatment which Weismann has shown, I am com- 

 pelled once more to dissent from him. His ideas have 

 recently been completely refuted by Max Kassowitz 

 (1902) in his General Biology, and Ludwig Plate in the 

 work I mentioned on the Darwinian principle of selec- 

 tion. We need not go into the details of the complicated 

 hypothesis as to the molecular structure of the plasm 

 which Weismann has framed in support of his theory of 

 heredity— his theory of biophora, determinants, ideas, 

 etc. — ^because they have no theoretical basis and are of 

 no practical use. But we must pass some criticism on 

 one of their chief consequences. In the interest of his 

 complicated hypotheses, Weismann denies one of La- 

 marck's most important principles of transmutation — 

 namely, the inheritance of acquired characters. 



When I made the first attempt in 1866 to formulate 

 367 



