USE-INHERITANCE AN E VI L. 1 29 



disappear in favour of enlarged hoofs. The 

 elephant's tusks would become smaller than its 

 teeth. Men would have callosities for sitting 

 on, like certain monkeys, and huge corns or 

 hoofs for walking on. Bones would often be 

 modified disastrously. Thus the condyle of the 

 human jaw would become larger than the body 

 of the jaw, because as the fulcrum of the lever 

 it receives more pressure. Some organs (like the 

 heart, which is always at work) would become 



inconveniently or unnecessarily large. Other 



. 



absolutely indispensable organs, which are com- 

 paratively passive or are very seldom used, 

 would dwindle until their weakness caused the 

 ruin of the individual or the extinction of the 

 species. In eliminating various evil results of use- 

 inheritance, natural selection would be eliminat- 

 ing use-inheritance itself. The displacement of 

 Lamarck's theory by Darwin's shows that the 

 effects of use-inheritance often differ from those 



K 



