192 THE THEORIES OF EVOLUTION 



due to disuse of the muscles of the ear, from the ani- 

 mals being seldom much alarmed, seems probable." 1 



The heredity of acquired characters, taking this term 

 in its broadest sense, was admitted by all naturalists 

 until the relatively recent time when Weismann re- 

 opened the question. Since then naturalists have 

 taken sides either with the Neo-Darwinians or with 

 the Xeo-Lamarckians. At the present day, the ma- 

 jority seems to be in favour of non-heredity, especially 

 as De Vries' new theory of mutation (see Chapter 

 XX) furnishes a new explanation that is perfectly 

 acceptable to those whom Darwin's theory of slight 

 variations does not absolutely satisfy. Many natural- 

 ists, however, have implicit faith in the heredity of ac- 

 quired characters. 



The question at issue is really a double question: 

 1 — Are the facts cited by the Xeo-Lamarckians to 

 prove that acquired modifications are inherited, real 

 facts and have they been interpreted properly? 

 2 — Can there be any hereditary transmission, in other 

 words, is there a processus by which an organic modifi- 

 cation due to the influence of the environment or to a 

 reaction against the environment can be transmitted 

 to the germ cells and reappear under the same form 

 in the sexual product? 



It was very necessary to formulate an accurate defi- 

 nition of the terms "innate characters" and "acquired 



i Dabwin. The Origin of Species, Chap. I, p. 10. 



