THE PAEAMECIUM AND ITS ALLIES 227 



the foregoing are the Sporozoa, 1 which are minute rod- 

 like organisms, occurring as parasites in the body of 

 various kinds of higher animals, especially in the food- 

 tract. They increase by transverse division of their rod- 

 like bodies ; but periodically they encyst, and divide into 

 numerous "spores," which, under favorable conditions, are 

 set free in great numbers. 



\ *': ;/?SiVr.Ar? '' 



- 





Jiiii ; fv 



( ^?iii^m^m0^^ n 



~- ^-iSSfS?;0;|Sssk 



FIG. 210. Amoeba, the proteus animalcule. Greatly magnified, n, the 

 nucleus; w. v, water vacuoles ; c. ?-', contractile vacuoles; /. v, food vacuoles. 

 E. B. Wilson, "The Cell." 



Of all Protozoa, probably the simplest is Amoeba. 2 This 

 type varies greatly in size, from 0.02 mm. to about 0.3 mm. 

 It appears as a clear, highly refractive body of changing 

 outline. The body does not look homogeneous when 

 viewed with a high power, but contains various granules 

 derived from ingested food, vacuoles of water, and a trans- 

 parent, slightly more dense, spherical or ellipsoidal body, 



1 0-7T6/OOS, spore ; fwoj/, animal. 



2 aioi3? alteration. 



