22 



COMPARATIVE PHYSIOLOGY. 



Multiplication of the species is either hy gemmation or by 

 fission. In the first case the nucleus divides and the frag- 



Fia.ffi'. 



Fig. 40. 



Fio. 36. 



Fios. 34 to 40.— In the figures d denotes disk ; o, 

 peristome; vc, contractile vacuole; vf, food- 

 vacuole; w, vestibule; c[, contractile fiber; 

 c, cyst; wc, nucleus; c^, cilium. 



Fig. 34.— a group of vorticellse showing the crea- 

 ture in various positions (A, 3). 



Fia. 35. — The same, in the extended and in the 

 retracted state. (Surface views.) 



Pig. 36.— Shows food-vacuoles; one in the act of 

 ingestion. 



Fig. 37. — A vorticella, in which the process of 

 multiplication by fission is begun. 



Fig. 38.— The results of fission; the production 

 of two individuals of unequal size. 



Fig. 39.— Illustration of reproduction by conju- 

 gation. 



Fig. 40.— An encysted vorticella. 



Fia.3S, 



ments are transformed into locomotive germs; in the latter 

 the entire animal, including the nucleus, divides longitudi- 

 nally, each half becoming a similar complete, independent or- 

 ganism. Still another method of reproduction is known. A 

 more or less globular body encircled with a ring of cilia and 

 of relatively small size may sometimes be seen attached to 

 the usual form of Vorticella, with which it finally becomes 

 blended into one mass. This seems to foreshadow the " sexual 



