iv WEISMANN'S CRITICISMS 225 



restricts his denial to the Metazoa ; but this is 

 assuming a physiological contrast to the unicellular 

 forms of life which it will not be easy to justify. On 

 the other hand, we possess, in the facts of domestica- 

 tion and cultivation, a large number of cases of 

 variation which occurs in every part due to environ- 

 ment, and transmitted by inheritance in various 

 degrees. Psychology affords similar instances : a 

 kitten which has never seen a dog is afraid from the 

 first moment it perceives one ; young birds of many 

 species instinctively fear the hawk and other birds of 

 prey, while remaining unaffected by the presence of 

 other birds. Are these not psychological " attitudes " 

 due to environment (acting on the mens of ancestors) 

 which have been transmitted by inheritance ; are 

 these not acquired characters / I would recommend, 

 in regard to this discussion, two recent papers : Mr. 

 J. A. Thomson's History and Theory of Heredity 

 (Proc. Roy. Soc. Edin., 1889), where the writer gives 

 his reasons for not accepting Weismann's extreme 

 views, and E. B. Poulton's Theories of Pleredity (Mid- 

 land Union of Natural History Societies, 1889). The 

 latter seems more favourably disposed to Weismann's 

 theory, which he has greatly contributed to spread 

 in England through his excellent translation of the 

 Essays on Heredity. 



