The Study of Animal Life part m 



more useful in surrounding minute food particles. To these root- 

 like processes, which are capable of very considerable, often almost 



constant, change, these 

 Protozoa owe their gen- 

 eral name of Rhizopods. 

 In contrast to the two 

 preceding types which 

 have definite boundaries 

 or "skins," the Rhizo- 

 pods are naked, and their 

 living matter may over- 

 flow at any point. 



As the Infusorians 

 are for the most part 

 provided with cilia from 

 which flagella differ only 

 in detail, we may speak 

 of the type as ciliated ; 

 the self-contained Gre- 

 garines, often wrapped 

 up within a sheath, we 

 may call predominantly 

 encysted ; while those 

 forms which are inter- 

 mediate between these 

 two extremes, and ex- 

 hibit outflowing pro- 

 cesses of living matter, 

 are called amoeboid in 

 reference to their most familiar type, the common Amoeba. 



But though the members of each class are characterised by the 

 predominance of one of the three phases of cell-life, they sometimes 

 pass from one phase to another. Thus the ciliated or the amoeboid 

 units may become encysted. 



Fig. 40. — A foraminifer (Polystomella strigillata) 

 with interlacing processes of the_ living matter 

 flowing out on all sides. Magnified 10 times. 

 (From Chambers's Encyclop. ; after Max 

 Schultze.) 



Fig. 41. — Protomyxa. 1, encysted ; 2, dividing into many units; 3, these escap- 

 ing as flagellate cells ; 4, sinking into an amoeboid phase ; 5, fusing into a 

 Plasmodium. (From Chambers's Encyclof. ; after Haeckel.) 



As the three phases represent the three physiological possibilities 



