420 



BIOLOGY OF THE PROTOZOA 



monas). Swimming types have a thickened periplast which may 

 be smooth as in Phialonema (Fig. 60, p. 110) or longitudinally 

 and spirally ribbed (Heteronema, Tropidoscyphus) . In one group 

 (Choanoflagellates) a protoplasmic collar surrounds the flagellum 

 (Fig. 178). 



Fig. 179. — Flagellates with suckers, from the ruffed grouse. A, C, normal forms 

 of Cyathosoma striatum; B, dividing form of same; D, normal form of Ptyehostoma 

 bonasae; E, beginning of unequal division of same; F, slender individual, without 

 sucker, resulting from unequal division. X 2400. (After Tyzzer, 1930; courtesy of 

 Am. Jour. Hyg.) 



The great majority of animal flagellates, however, have become 

 adapted to the anaerobic conditions accompanying a parasitic mode 

 of life and these flagellates have become a vital factor in the hygienic 

 and economic relations of man, other animals and some plants (see 

 Chapter X, p. 352). Some parasitic forms have developed suckers 

 for attachment (e. g., Cochlosomidae, Fig. 179), 



