PLANT-ANIMALS, OR ZOOPHYTES. 151 



as little technicality as possible, some general idea of 

 the zoophyte animals, and the homes they inhabit. - 

 We may premise that the animals themselves 

 follow closely the type of the common Fresh-water 

 Hydra, and hence, by studying either the red or 

 green hydra of our " Ponds and Ditches," we shall 



FIG. 23. FRESH-WATER HYDRA (a b adults, c ^young). 



obtain a very fair idea of the hydra-shaped (hydroid) 

 polypes of the marine zoophytes. There is, how- 

 ever, one important difference, which must be noted 

 at once, in order to prevent any confusion of ideas. 

 The Fresh-water Hydra (fig. 23), is solitary, not grow- 

 ing in colonies, like its marine cousins, although three 



