4 General Morphology o£ the Protozoa 



conditions and activities of the organism. Even the nature and quantity 

 of the available food may influence form as well as size of the body. Such 

 a relationship is striking in Tetrahymena vorax (Fig. 1. 1) when strains 

 are fed on different diets (118). In addition to the usual variations, attrib- 



Fig. 1. 1. Influence of diet on form and size in Tetrahymena vorax. 

 A. Organism from young broth culture (saprozoic nutrition). B. Speci- 

 men from older broth culture. C. A ciliate fed on Aerobacter cloacae. 

 D. A ciliate fed on killed Tetrahymena geleii. E. A large carnivore from 

 a culture fed living T. geleii. F. A carnivore after transfer to a culture 

 of living yeast. Ingested food, peristomial area, and contractile vacuole 

 are indicated diagrammatically but cilia are not shown. x450 (after 

 Kidder, Lilly, and Claff). 



utable to environmental or inherent factors, dimorphic and polymorphic 

 life-cycles include two or more different morphological stages. Naegleria 

 gruberi (Chapter V), for example, exhibits both flagellate and amoeboid 

 stages. Although adaptive trends may be assumed, specific correlation of 

 form with habitat is impossible in many instances. Yet certain generaliza- 



