Chapter 10 

 Order 4 Euglenoidina Blochmann 



THE body is as a rule elongated; some are plastic, others have a 

 definite body form with a well-developed, striated or variously 

 sculptured pellicle. At the anterior end, there is an opening 

 shrough which a flagellum protrudes. In holophytic forms the 

 to-called cytostome and cytopharynx, if present, are apparently 

 not concerned with the food-taking, but seem to give a passage- 

 way for the flagellum and also to excrete the waste fluid matters 

 which become collected in one or more contractile vacuoles 

 located around the reservoir. In holozoic forms, a well-developed 

 cytostome and cytopharynx are present. Ordinarily there is only 

 one flagellum, but some possess two or three. Chromatophores 

 are present only in the majority of the Euglenidae and absent 

 in the other two families. They are green, vary in shape, such as 

 spheroidal, band-form, cup-form, discoidal, or fusiform, and 

 usually possess pyrenoids. Some forms may contain haemato- 

 chrome. A small but conspicuous stigma is invariably present 

 near the anterior end of the body in chromatophore-bearing 

 forms. 



Reserve food material is the paramylon body, fat, and oil, 

 the presence of which depends naturally on the metabolic condi- 

 tion of the organism. The paramylon body assumes diverse forms 

 in different species, but is, as a rule, constant in each species, and 

 this facilitates specific identification to a certain extent. Nutrition 

 is holophytic in chromatophore-possessing forms, which, however, 

 may be saprozoic, depending on the amount of light and organic 

 substances present in the water. The holozoic forms feed upon 

 bacteria, algae, and smaller Protozoa. 



The nucleus, as a rule, is large and distinct and contains almost 

 always a large endosome. Asexual reproduction is by longitudinal 

 fission; sexual reproduction has been observed in a few species. 

 Encystment is common. The majority inhabit fresh water, but 

 some live in brackish or salt water, and a few are parasitic in 

 animals. 



203 



