i82 THE POPULAR SCIEyCE MONTHLY. 



motlier 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 transforma- 

 tion." * 



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 propound- 

 ed, 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." f 



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 in- 

 equalities of nutrition (which at bottom are the same thing) mod- 

 ify the germ cells, he denies that these two facts have any con- 

 nection with each other. Obvious as it is that the species becomes 

 modified to suit the changing environment just as does the indi- 

 vidual, 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 in- 

 dictment against Nature, " who," he says, " always manages with 

 economy." X I^ seems far more logical to argue from the econ- 

 omy 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 nutri- 

 tion" 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 distinc- 

 tion 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 



* Neo-Darwinisra and Neo-Laraarckism, etc., p. 49. 

 f Germ-Plasm, p. 462, % Ibid., p. 63. 



