12 BIOLOGICAL SOCIETY OF WASHINGTON. 



pace with the rest of the science, and I felt that if compelled 

 to listen to views growing chiefly out of that narrow specialty, 

 it was in some degree its own fault. But in view of the fact 

 that the Society saw fit to repeat its mistake, and that I last 

 year presented the problems of botany and its geologic history, 

 there seems no escape from that duty which still confronts me 

 of closing with the great problem of heredity which continues 

 to occup3' the foreground of all biological discussion. 



There is strictly speaking only one prominent question be- 

 fore the biological world and that is the question whether qual- 

 ities that are acquired after birth are capable of being trans- 

 mitted to descendants. Darwinism in its original entirety, as 

 expounded by Darwin himself, admits such transmission. But 

 by the new school of Neo-Darwinists this is denied. On the 

 other hand Lamarckism, as expounded by Lamarck, explains 

 all change through the tran.smission of functionally acquired 

 characters, the law of natural selection not having been per- 

 ceived by lyamarck. But Neo-Lamarckism, as I understand it, 

 while recognizing natural selection as the more potent of the 

 two agencies, also recognizes that the increments of change im- 

 pressed upon individuals during their lifetime or brought about 

 by individual efforts or habits are also perpetuated in some 

 measure through heredit}^ and form an important factor in 

 the general process of organic development. 



STATUS OF THE PROBLEM. 



From the appearance of the Origin of Species in 1859 until 

 within the past four or five years it had been the opinion of 

 nearly all naturalists that the existing forms of animals and 

 plants were the result mainly of two cooperating causes, one 

 of which may be called functional and the other selective. The 



