PLASMODROMA, MASTIGOPHORA, CHRYSOMONADIDA 85 



(rarely green or bluish) and usually discoid, though sometimes 

 reticulated. The products of metabolism are refractile bodies, 

 known collectively as leucosin (probably carbohydrates), fats 

 and oils. Starches have never been found in them. The flagella, 

 usually one or two in number, are planted at or near the 

 anterior end of the body, with a stigma near the insertion point, 

 as a rule, when there is but one flagellum. 



Many Chrysomonadida are able to form pseudopodia for ob- 

 taining food materials, which vary among different species. 

 Nutrition, though chiefly holophytic, is often holozoic or sapro- 

 zoic also. Contractile vacuoles are invariably found in fresh- 



Fig. 29 Diagram showing the development of Chromulina. X about 200. 

 (After Kuhn, modified), a, encystment; b, fission; c, colony for- 

 mation; d, palmella formation. 



water forms. They are ordinarily of simple structure, although 

 a few of them have rather complicated systems. 



Under conditions not fully understood, the Chrysomonadida 

 transform themselves into a rounded stage known as the pal- 

 mella phase and undertake metabolic activities as well as 

 multiplication (Fig. 29). Asexual reproduction is usually by 

 longitudinal division during either the motile or the palmella 

 stage. Incomplete separation of the daughter individuals fol- 

 lowed by repeated fission, results in numerous colonial forms of all 

 three types mentioned elsewhere (p. 51). Some resemble higher 

 algae very closely. Sexual reproduction is entirely unknown in 

 this group. Encystment occurs commonly among the chryso- 



