l62 



ZOOLOGY 



Class II. Mastigophora {whip bearers). Types: Euglena, Chilomonas, Volvox, 

 Trypanosoma. Active Protozoa which may be simple or colonial. They bear one 

 or more large lashes or flagella. The trypanosomes are blood-parasites. 



Class III. Infusoria {in infusions). — Types: Paramecium, Stentor, Vorticella. 

 Predominantly active Protozoa, usually without shell, but with distinct cortical 

 portion from which project permanent vibratile threads of protoplasm (cilia or 

 tentacles), from the possession of which the sub-classes are named. There is 



Fig. 75. 



Fig. 75. jlcffnomma, a radiolariaii with a shell and no mouth, ii, whole animal with a portion 

 of two spheres of shell removed. B. section, showing relation of protoplasm to the skeleton, c. 

 central capsule; n, nucleus; p, protoplasm; o, openings through which the pseudopodia extend 

 (Prom Parker and Haswell.) 



usually a permanent mouth. The nucleus is always present and assumes a great 

 variety of shapes. The Infusoria are typically free-swimming, but many are 

 capable of attachment by a contractile stalk, to foreign objects {Vorticella). 

 Reproduction is normally by equal division, but budding and spore formation 

 occur. Conjugation is common, and may be either temporary or permanent. 



Class IV. Sporozoa {spore animals). — Types: Plasmodium vivax, Gregarina. 

 Protozoa predominantly passive in habit, parasitic, with no pseudopodia, and no 

 cilia in the adult. Remarkable for encysted resting stages and spore formation. 

 Conjugation often precedes the formation of the cyst. 



202. Place in Nature. — Protozoa are an important element 

 in the food of many aquatic animals. Despite their minute 

 size, their immense numbers and universal distribution make 

 them important. Together with bacteria they serve to save 

 for the organic world much decaying material which no other 

 animals could utilize. The bacteria decompose organic matter 

 and the Protozoa devour bacteria. They in turn become food 

 for higher animals. We have seen that there are green forms 



