222 



COMPARATIVE ANATOMY 



A living Hydra adheres pretty firmly by its proximal end 

 often called the foot, or, better, the basal disc to the object to 

 which it is attached. It is not permanently fixed, however, but 



Fig- 47- 



On the left hand a specimen of Hydra fusca, fully extended ; 

 tt, testes ; mi, ovum with horny case. On the right hand a 

 specimen of Hydra viridis, half extended ; 6, a bud. 



can detach itself and move slowly from place to place, either 

 creeping along by means of its tentacles, or by a series of 

 movements resembling those of the looping caterpillar. In the 

 latter case, the body is extended as far as possible and bent 



