OUR FUTURE COURSE 223 



merit. In view of the fact that they have as great 

 logical appeal as the mutations which have de- 

 manded so much of our attention, and even more 

 harmony with the apparent course of evolu- 

 tion, they seem worthy of more attention and more 

 careful and thorough experimentation than have 

 hitherto been accorded them, but we cannot expect 

 greater success in our experiments than has re- 

 sulted in the past unless they are undertaken with 

 a clear idea of the probable part of individual 

 response in evolution. No one factor in so complex 

 a process can be responsible for all of the results, 

 and until we know all factors and recognize their 

 interaction we must remain ignorant of the total 

 process. 



Any experiment which embodies the essential 

 factors of individual response to environment as 

 stated above will give useful results, but for the 

 thorough investigation of the problem we must 

 first determine the nature of individual response 

 through a reasonably long succession of genera- 

 tions. Response is cumulative in the individual, 

 but is there any possibility of cumulative response 

 through several generations? Guyer and Smith 

 have given us the nearest approach to a sound 

 investigation of this question in their studies of 

 typhoid agglutinins in rabbits.^ "The young of 

 immunized mothers can, without further immuni- 



' Jn. Inf. Diseases, Vol. XXX, (6), p. 498, 1923. 



