68 HEREDITY 



. . . to type." This is Galton's law of regression 

 towards mediocrity, already discussed. It follows 

 from it that where there is much in-breeding the 

 weight of mediocrity will be less, and the peculiari- 

 ties of the breed will be accentuated. The present 

 German Emperor might have had 4096 ancestors in 

 the twelfth generation ; but, owing to inter-marriages 

 {i.e. in-breeding) probably had only 533. The weight 

 of mediocrity is less, the tendency to regression less, 

 and the distinctive characters of his race thus more 

 likely to be preserved. 



CHAPTER IX 



THE THEORIES OF HEREDITY 



In this very brief chapter we may indicate, side by 

 side, the three theories of heredity which are elsewhere 

 frequently alluded to. By theories of heredity we 

 mean explanations of the actual sequence of events 

 which results in the reproduction of like by like. 

 Of these there are but three worthy of mention. 



The oldest is Darwin's theory of pangenesis, Avhich 

 supposed that every body-cell produces " gemmules " 

 characteristic of it, which are somehow gathered 

 together in the germ-cells. When these develop, 

 the gemmules reproduce, in the body of the new 

 individual, the characters of those cells of the parent 

 from which they were derived. On this theory 

 nothinsr could be more natural than the trans- 

 mission of acquirements. But it is absolutely incom- 

 patible with the facts known to modern embryology, 



