200 EVOLUTION 



congenital variations are favoured and given 

 time to get a hold on the organism, and are 

 thus enabled by degrees to reach the fully 

 adaptive level." 



Yet another consideration. Although we 

 do not know of any case of the transmission 

 of a modification as such, or even in a repre- 

 sentative degree, we, of course, agree with 

 Weismann in admitting that modifications 

 may have secondary effects on the germ- 

 cells, and thus on the offspring. In this way 

 "nurture" may come to have a racial im- 

 portance. Nor can w^e forget that the en- 

 vironment of mammalian mothers is bound 

 to have an influence on the unborn young, 

 which shares the maternal life so closely. 

 Apart from the "mysterious wireless teleg- 

 raphy of antenatal life," there is a sharing 

 of the diffusible substances carried by the 

 blood. 



The Role of Function. — We cannot go 

 back to the cruder forms of the Lamarckian 

 theory, and believe that the giraffe length- 

 ened its neck by stretching it; yet we must 

 beware of taking too simple a view of what 

 function implies. What are the certainties.^ 

 We know that development — the expression 

 of an inheritance — demands functional as 

 well as environmental stimuli. Practice 

 makes an organ possible. Without exercise 



