THK n.EMOFLAGELLATKS. 



153 



The Hasmoflagellates possess either one or two flagella^ 

 inserted into tlie body, with few exceptions^ at or near its 

 anterior end. When there are two flagella^ one is free and 

 directed forwards; the other is attached for the greater part 

 of its length to the side of the body, by means of an undu- 

 lating membrane, and terminates ultimately in a free portion 

 directed backwards. When only one flagellum is present, it 

 is invariably attached in this manner, but the flagellum is 



A B 



Fig. 1. — "Unclulina laiiarum," Laiikester, 1871. In B, 

 the nucleus is shown. (From Lankester.) 



probably not to be considered homologous in all these cases. 

 In certain forms, which are to be derived from a Monadine 

 ancestor, it is, of course, the single anterior flagellum that is 

 represented; in others, however, which are rather to be re- 

 garded as descended from a Heteromastigine ancestor, it is the 

 trailing, posteriorly-directed flagellum that persists. There 

 are two nuclear bodies, one, the trophonucleus, regulating 

 the trophic life of the cell, the other, the kinetonucleus, 

 directing its kinetic activities. 



The most general method of reproduction is by binary. 



