20 



ZOOLOGY. 



Class I. — IItdkozoa. 



Characters of Hydrozoans. — The common Hydra (Fig. 18) 

 may be found in fresh-water ponds attached by its liase to tlie 

 t 



WiQ. \i.— Hydra fusca, vnOx two young (a c) budding from it: 6, the base- s, the 



digestive cavity; (, tentacles. Magnifled. 



under side of the leaves of aquatic ])lai]ts. It .-^s not fixed 

 permanently, but can move freely about. It is \erv small 

 just large enough to be seen without a magnifyino class- 

 it is usually pale green, but is sometimes brownt The 



