HYDRA 



251 



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

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

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



Fig- 53- 



On the left hand a specimen of Hydra jrusca t fully extended ; 

 it, testes ; ov, ovum with horny case. On the right haml a 

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



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 

 downwards till the mouth touches the weed or other object to 

 which the animal is attached. The mouth being fixed to the 



