Chapter 11 

 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 through 

 which a flagellum protrudes. In holophytic forms the so-called cyto- 

 stome 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 near 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 in the majority of the Eu- 

 glenidae, but absent in 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 

 haematochrome. A small but conspicuous stigma is invariably pres- 

 ent 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 condition 

 of the organism. The paramylon body assumes diverse forms in dif- 

 ferent 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 sub- 

 stances present in the water. The holozoic forms feed upon bacteria, 

 algae, and smaller Protozoa. 



The nucleus is, as a rule, 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. En- 

 cystment is common. The majority inhabit fresh water, but some 

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

 Taxonomy (Mainx, 1928; Hollande, 1942, 1952a); Jahn, 1946; Pring- 

 sheim, 1950. 



With stigma Family 1 Euglenidae (p. 294) 



Without stigma 



With 1 flagellum Family 2 Astasiidae (p. 302) 



With 2 flagella Family 3 Anisonemidae (p. 303) 



293 



