EUGLENOIDIDA, CHLOROMONADIDA 117 



The nucleus, as a rule, is large and distinct and contains al- 

 most always a large endosome. Asexual reproduction is by 

 longitudinal fission; sexual reproduction has been observed in 

 a few species. Encystment is wide-spread. Most members of 

 the group inhabit fresh water, but some live in brackish or salt 

 water, and a few are parasitic in animals. 



Following Calkins, the order is here divided into three 

 families: 



With chromatophores and stigma Family 1 Euglenidae 



Without chromatophores or stigma 



With one flagellum Family 2 Astasiidae 



With two flagella .Family 3 Heteronemidae 



Family 1 Euglenidae Stein 



Body plastic ("euglenoid"), but, as a rule, more or less 

 spindle-shaped during movement. The majority possess a 

 single flagellum (with the exception of Eutreptia and Euglena- 

 morpha) which arises in an opening at the anterior end. Green 

 (sometimes red) chromatophores and stigma occur, though in 

 some cases absent. Metabolic products are oil and paramylum. 

 Asexual reproduction by longitudinal fission in either the active 

 or the resting stage. Mostly freshwater inhabitants, but some 

 marine. 



Genus Euglena Ehrenberg. Body short or elongated spindle, 

 cylindrical, or band-form. The pellicle is marked in some forms 

 by longitudinal or spiral striations. In forms in which the 

 pellicle is not well developed, the body is highly plastic. Ac- 

 tively moving individuals are ordinarily spindle-shaped, while 

 those remaining in one place may show considerable changes 

 of form. Some species are regularly spirally twisted. Stigma 

 is usually located near the anterior end. Chromatophores are 

 numerous and discoidal, bandform, or stellate. Pyrenoids are 

 sometimes present; they may or may not be surrounded by 

 amyloid sheath. Metabolic products are paramylum bodies 

 which may be two in number, one being located on either side 

 of the nucleus, and rod-like to ovoid in shape; numerous and 

 small ovoidal; or discoidal and scattered throughout. The con- 

 tractile vacuoles are very small and arranged around the reser- 

 voir located near the anterior end. 



