472 PRIMARY FACTORS OF ORGANIC EVOLUTION. 



ally propounded this doctrine. Galton's language ^ is 

 as follows : 



"It is said that the structure of an animal changes 

 when he is placed under changed conditions ; that his 

 offspring inherit some of his change ; and that they 

 vary still further on their own account, in the same 

 direction, and so on through successive generations 

 until a notable change in the congenital characteristics 

 of the race has been effected. Hence, it is concluded 

 that a change in the personal structure has reacted on 

 the sexual elements. For my part, I object to so gen- 

 eral a conclusion, for the following reasons. It is 

 universally admitted that the primary agents in the 

 processes of growth, nutrition, and reproduction, are 

 the same, and that a true theory of heredity must so 

 regard them. In other words, they are all due to the 

 development of some germinal matter, variously lo- 

 cated. Consequently, when similar germinal matter 

 is everywhere affected by the same conditions, we 

 should expect that it would be everywhere affected in 

 the same way. The particular kind of germ whence 

 the hair sprang, that was induced to throw out a new 

 variety in the cells nearest to the surface of the body 

 under certain changed conditions of climate and food, 

 might be expected to throw out a similar variety in the 

 sexual elements at the same time. The changes in 

 the germs would everywhere be collateral, although 

 the movements where any of the changed germs hap- 

 pen to receive their development might be different." 



This is the first statement of the doctrine of diplo- 

 genesis with which I have met, and it appears to fur- 

 nish the most rational basis for the investigation into 

 the dynamics of the process. 



1 Contemporary Review, 1875, pp. 343-344 ; Proc. Royal Society, 1872, No. 136. 



