ON ANIMAL LIFE 



109 



Fig. 4 represents the Medusa or free form 

 of this beautiful species. 



If we pass to another 

 great group of Zoophytes, 

 that of the Jelly-fishes, 

 we have a very similar 

 case. For our first knowl- 

 edge of the life-history 

 of these Zoophytes we 

 are indebted to the Nor- 

 wegian naturalist Sars. 

 Take, for instance, the 

 common Jelly-fish (Me- 

 dusa aurita) (Fig. 5) of 

 our shores. 



The egg is a pear-shaped body (i), covered 

 with, fine hairs, by the aid of which it swims 

 about, the broader end in front. After a 

 while it attaches itself, not as might have 

 been expected by the posterior but by the 

 anterior extremity (2). The cilia then dis- 

 appear, a mouth is formed at the free end, 

 tentacles, first four (j), then eight, and at 

 length as many as thirty (4), are formed, and 

 the little creature resembles in essentials the 

 freshwater polyp (Hydra) of our ponds. 



Fig. 4. — BougaiDvillea 

 fruticosa. Medusa-form. 



