192 



ZOOLOGY 



Ciliates or 

 Infusoria 



tractile vacuole, and also frequently various objects taken 

 in as food. Many other rhizopods form shells of 

 various kinds, often looking like little jars or flasks, or 

 flattened and circular, like buttons. In one genus 

 (Quadrulella) the shell is composed of quadrangular 

 plates ; in another (Difflugia) it consists principally of 

 sand grains united together by a secretion of the animal. 

 In one family the pseudopodia are threadlike. 



Related to the Rhizopoda are the Heliozoa or "sun 

 animalcules," a common representative having a 

 spherical form and long, raylike pseudopodia, resem- 

 bling conventional pictures of the sun. The marine 

 Radiolaria, already mentioned, are related to the 

 Heliozoa. 



7. The Infusoria move by means of cilia (singular, 

 c ilium), which are very fine eyelash-like projections 

 from the body, moving like the oars of a boat and caus- 

 ing the animal to be rapidly propelled through the 

 water. Reproduction is usually by simple transverse 



A 



Drawing by R. Weber 



FIG. 41. Types of Protozoa. A, Shell of Lagena (Foraminifera) Marine ; B, Stylo- 

 cephalus, a gregarine parasitic in beetles ; C, Quadrulella, a freshwater Rhizopod. 

 All much magnified. 



