256 BIOLOGY OF THE PROTOZOA 



as to its reproduction by division in different forms. In Euglena 

 according to Zumstein (1900) it divides longitudinally, whereas in 

 Uroglena according to Iwanoff (1899) it is newly formed at each 

 division of the cell. 



Trichocysts.— Trichocysts giving rise to gelatinous threads on irri- 

 tation and possibly functioning as adhering organoids are found in 

 the cortex of some of the Chloromonadida. Much more complex 

 cnidocysts are present in some of the Dinoflagellida {Ponchetia, 

 Polykrikos) . 



Nutrition.— Nutrition in Phytomastigoda, as indicated by the 

 presence of chromatophores and chlorophyll, is essentially autotro- 

 phic. Only a few types, however, are constrained by reason of an 

 unbroken cellulose covering to live exclusively by autotrophic means 

 (Phytomonadida) . In all other groups more or less well-defined 

 areas for absorption of fluid or solid substances are present and we 

 find a combination of autotrophic with either saprophytic, saprozoic, 

 or holozoic nutrition. In many of the Chrysomonadida the tem- 

 porary or permanent pseudopodia serve as active agents in food- 

 getting. Parasitic, or better, commensal and symbiotic types are 

 not unknown, species of Eiiglena and Phacvs, for example, are 

 usually found in the alimentary tract of tadpoles and frogs (Hegner). 

 The entire group of Blastodinidse have become highly modified 

 through parasitism. 



Products of destructive metabolism stored up in the cell are fre- 

 quently characteristic enough to be useful in classification. Thus 

 starch is never found in Chrysomonadida, but leucosin, oils and 

 fats are present. In Cryptomonadida starch-like products are 

 abundant but true starch is rarely present. In Eiiglenida para- 

 mylum is characteristic and in the Phytomonadida true starch. 

 In many cases, but not of necessity, the carbohydrates are manufac- 

 tured in connection with definite bodies, the pyrenoids. 



While the Phytomastigoda are typically motile organisms, moving 

 by means of flagella, the majority of them differ from other motile 

 Protozoa in having the ability to discard their flagella and still con- 

 tinue an active metabolic life. Such phases are not to be confused 

 with encystment, which involves im])ervious walls, but while in 

 this immobile state feeding and reproduction ma,y continue normally. 

 The Rhizochrysidse and Phytodinida? include forms in which flagella 

 have never been seen and apparently represent forms in which such, 

 usually temporary stages of other types, have become permanent. 

 Not infrequently and while in this aflagellate stage, the cells secrete 

 a gelatinous enveloping substance and in this, with reproduction, 

 typical Palmella-like aggregates are formed. Such quiescent phases 

 are common in all orders of the group with the exception of 

 the Chloromonadida and become the dominant phase in the life 

 history of the Chrysocapsinte, Phseocapsinse, Phytodinidse, and 



