58 HEREDITY AND ENVIRONMENT 



that it responds more rapidly and more ac- 

 curately than an untrained muscle; and the 

 nervous mechanism through which the stimu- 

 lus is transmitted also becomes trained in the 

 same way. Indeed such training is probably 

 chiefly a training of the nervous mechanism. 

 The skill of the pianist, of the tennis player, 

 of the person who has learned the difficult art 



Fig. 20. Dionaea muscipula (Venus' Fly-tkap). Three 

 leaves showing marginal teeth and sensitive hairs (SH). The 

 leaf at the left is fully expanded, the one at the right is closed. 



