2C2 



NATURE STUDY IN SCHOOLS. 



Locomotion is accomplished in the hydra either by the animal sliding 

 along its base or foot, or by the animal grasping objects with its tentacles 

 and drawing itself along. A rare method is by bending over, grasping some 

 object, which is on a level with its foot, with its tentacles. The body is then 

 straightened, when the hydra stands, mouth down, on its head. The body 

 is then bent down in the opposite direction, the foot takes hold and the an- 

 imal rights itself, having turned a complete summersault. 



Hydras are, under some circumstances, very tenacious of life, and although 

 it is probable they seldom, or never, propagate by spontaneous division, they 

 miy be cut into several pieces, each of which will produce a perfect hydra. 

 Many interesting experiments have been made upon them ; one of the most 



Fig. 129. 



Fig. 130. 



Alternation of generation in bell polyp. 



Alternation of generation in Millipore. 



noteworthy of which is the inverting of the body by thrusting a wire into 

 the mouth. When thus turned, literally wrong side out, the hydra so treated 

 lived in that way and digested its food with what once its outer wall. The 

 hydra can withdraw its tentacles into the body. 



Hydras occur in abundance in many ditches, pools and river coves, but 

 rarely in swiftly flowing water. I have found three species in this vicinity,, 

 of which two, a pale brown species, and a smaller green species, are the 

 most common. They occur clinging to submerged sticks and water plants 

 from May until the ice closes over the water in late autumn or eaily win- 

 ter. 



