OF VORT1CELLA DESCRIBED. 41 



is known that many fixed zoophytes, and even some 

 plants, produce free swimming germs or spores, which 



Fig. 1. 



afterwards become fixed, and grow up into forms like 

 those which produced them. In some of the branch- 

 ing zoophytes (Coryne, Sertularia, &c.), the germs are 

 exactly like little medusae, being small, gelatinous 

 cups fringed with tentacula, by means of which they 

 twitch themselves along with surprising agility. In 

 this Vorticella, however, it is more like one of the 



