148 DOCTRINE OF EVOLUTION 



discoveries, the Lamarckian doctrine, which teaches 

 that acquired non-congenital characters are trans- 

 mitted, seems to be ruled out. I would not lead you 

 to believe that the matter is settled. I would say only 

 that the non-transmission of racial mutilations, nega- 

 tive breeding experiments upon multilated rats and 

 mice, the results of further study of supposedly trans- 

 mitted immunity to poisons — that all these have led 

 zoologists to render the verdict of ''not proved." The 

 future may bring to light positive evidence, and cases 

 like Brown-Sequard's guinea-pigs, and results like 

 those of MacDougal with plants, and of Tower with 

 beetles, may lead us to alter the opinion stated. But 

 as it stands now most investigators hold that there 

 are strong general grounds for disbelief in the principle, 

 and also that it lacks experimental proof. 



The explanation of natural evolution given by Dar- 

 winism and the principles of Weismann, Mendel, and 

 De Vries, still fails to solve the mystery completely, 

 and appeal has been made to other agencies, even 

 to teleology and to "unknown" and "unknowable" 

 causes as well as to circumstantial factors. A com- 

 bination of Lamarckian and Darwinian factors has 

 been proposed by Osborn, Baldwin, and Lloyd Morgan, 

 in the theory of organic selection. The theory of 

 orthogenesis propounded by Naegeli and Eimer, now 

 gaining much ground, holds that evolution takes place 

 in direct lines of progressive modification, and is not 

 the result of apparent chance. Of these and similar 

 theories, all we can say is that if they are true, they are 



