Fig. 49. — Hydra. 



A, Two living specimens of H. viridis attached to a bit of weed. 

 The larger specimen is fully expanded, and shows the elongated body 

 ending distally in the hypostome {hyp), surrounded by tentacles (/), and 

 three buds {bd\ bd', hd^) in different stages of development : a small 

 water-flea {a) has been captured by one tentacle. The smaller specimen 

 (to the right and above) is in a state of complete retraction, the tentacles 

 (t) appearing like papillse. 



B, H. fiisca, showing the mouth (mth) at the end of the hypostome 

 (hyp), the circlet of tentacles (/), two spermaries {spy), and an ovary 

 (ovy). 



C, a Hydra creeping on a flat surface by looping movements. 



D, a specimen crawling on its tentacles, 

 (c and D after W, Marshall.) 



