HYDRA 



265 



poison, and soon conveyed to the Hydra's mouth. The 

 principal food of Hydra consists of small worms and the 

 smaller Crustacea, such as Daphnia and Cydops. 



Fig. 254. — A colony of Cordylophora l(wvstris, on a shell of Mytilus. For 

 clearness, a number of the erect branches are cut off at the stolon, a, very 

 young shoot without lateral branches ; b, young stock with lateral branches 

 but no gonophores ; c, a stock with gonophores on lateral branches ; 

 d, fully grown stock with lateral stems. After Schulze. 



Fresh-water Hydroids are of extremely few kinds. Hydra 

 was once regarded as the only instance, but others are now 

 known. One of these, called Cordyloph'ora (Fig. 254), is found 

 chiefly in brackish water or in fresh water near the coast. 

 Like many of the marine hydroids, Cordylophora produces its 

 young in special capsules, called gonophores, which are rudi- 

 mentary jellyfishes (Fig. 254, c). The young become free when 



