THE AMCEBA, HYDRA, AND OTHER SIMPLE ANIMALS n? 



nuclei and two contractile vacuoles, the many fixed cilia, 

 and the definite form of the body, which is inclosed by a 

 thin skin or cell- wall, are all slight advances toward a 



Fig. So. Fk;. Si. 



Fig. So. — Paraniccchim sp.; buccal grnove at right. (Greatly magnified; 



from life.) 

 F'IG. Si. — Vorticella sp. ; one individual with stalk coiled, and one with 



stalk extended. (Greatly magnified; from life.) 



more complex make-up. But ParamcEcium is still a sin- 

 gle cell. Make a drawing of a Paramoecium. 



Another common one-celled animal, and a curious and 

 interesting one, is the bell animalcule (Vorticella) (fig. 8i). 

 The individuals of this group live together in colonies, a 

 single colony appearing to the naked eye as a tiny, 

 whitish, mould-like tuft or spot on the surface of some 



