4o8 HISTORY OF THEORIES 



Jager's Theory. — The next theory — Jager's — is difficult to 

 summarise, partly because of its technical character, partly 

 because the author does not appear to be quite consistent in his 

 statement of it at different times. The main points, under the 

 present section, are as follows : 



(i) Each organ and tissue contains, along with the molecules 

 of its albumen, a specific " scent-stuff " (Duft- und 

 Wiirzestoff). 



(2) In hunger and similar experience the albumen liberates 



the " scent-stuft," which penetrates through the body as 

 fatty acids, ethers, etc. 



(3) These are specially attracted to the reproductive cells, 



which, when mature, are thus specialised by the reception 



of scent-stuff, and have in their protoplasm vires forma- 



tivcs enough to reproduce a new organism like the 



parent. 



It will be seen later on that this hypothesis of chemical 



pangenesis is not the most important contribution made by 



Jager to the theory of heredity. 



Galton's Modified Theory of Pangenesis. — From experi- 

 ments on the transfusion of blood, Mr. Francis Galton was led 

 to conclude that " the doctrine of pangenesis, pure and simple, 

 is incorrect." But he did more than urge serious objections 

 against Darwin's theory ; he formulated one of his own, to 

 which, with the exception of Prof. Herdman, subsequent in- 

 vestigators do not appear to have attached sufficient import- 

 ance. The very important part of Galton's theory will be 

 discussed in its proper place ; it is not included in the series of 

 pangenetic hypotheses. Galton is, in fact, one of the numerous 

 biologists who have suggested the continuity of the germinal 

 protoplasm. He is included at this stage, however, because 

 he admitted as a subsidiary hypothesis a limited amount of 

 pangenesis. To account for those cases which suggest that 

 characters acquired by the individual parent are " faintly 



