122 



THE IDEAL TYPES OF THE 



.'/- 



met 



en 



c vtc 1 h ma 



Fig. 57. 



G 



en g we </ nc- ma 



c en nc 1 



G 



Fig. 62. 



then does the Notonecta invariably keep his back in one direction, i. e., down- 

 wards, when his terra firma, the water, is all around him ? This is enough to 

 show that the matter of up and down has nothing whatever to do with the rela- 

 tive position of the organs of animals. 



