92 



PROTOZOOLOGY 



globules of Colpidium are digested by Amoeba proteus and trans- 

 formed into fatty acid and glycerine which unite and form neutral 

 fat. 



The indigestible residue of the food is extruded from the body. 

 The extrusion may take place at any point on the surface in many 

 Sarcodina by a reverse process of the ingestion of food. But in pelli- 

 cle-bearing forms, the defecation takes place either through the 

 cytopyge located in the posterior region of the body or through an 

 aperture to the vestibule (in Carchesium). Permanent cytopyge is 

 lacking in some forms. In Fdbrea salina, Kirby (1934) noticed that a 

 large opening is formed at the posterior end, the contents of food 

 vacuoles are discharged, and the opening closes over. At first the 

 margin of the body is left uneven, but soon the evenly rounded out- 

 line is restored. The same seems to be the case with Spirostomum 

 (Fig. 37), Blepharisma, etc. 



Fig. 37. Outline sketches showing the defecation process in 

 Spirostomum ambiguum (Blattner). 



Holophytic (autotrophic, phytotrophic) nutrition. This is the type 

 of nutrition in which the Protozoa are able to decompose carbon 

 dioxide by means of chlorophyll contained in chromatophores (p. 78) 

 in the presence of the sunlight, liberating the oxygen and combining 

 the carbon with other elements derived from water and inorganic 

 salts. The pyrenoids (p. 79) are inseparably connected with the 

 reserve carbohydrate formation in this nutrition. Aside from the 

 Phytomastigina, chromatophores were definitely observed in a cili- 

 ate Cyclotrichium meunieri (Fig. 268, o) by Powers. In a number of 

 other cases, the organism itself is without chromatophores but is 

 apparently not holozoic, because of the presence of chlorophyll- 

 bearing organisms within it. For example, in the testacean Paulinella 

 (Fig. 182, c) in which occur no food vacuoles, chromatophores of 

 peculiar shape are always present. The latter appear to be a species 

 of alga which holds a symbiotic relationship with the testacean, and 

 perhaps acts for the sarcodinan as the chromatophores of the Phyto- 



