208 PROTOZOOLOGY 



in diameter; when present in abundance, the organism gives an of- 

 fensive odor to the water (Calkins). 



U. europaea Pascher. Similar to the last-named species; but 

 chromatophores 2; cells up to 7/i long; colony 150-300^ in diameter. 



Genus Cyclonexis Stokes. Wheel-like colony, composed of 10-20 

 wedge-shaped individuals; young colony funnel-shaped; chromato- 

 phores 2, lateral; no stigma; reproduction and encystment unknown; 

 fresh water. 



C. annularis S. (Fig. 92, e). Cells 11-14^ long; colony 25-30^ in 

 diameter; in marshy water with sphagnum. 



Genus Dinobryon Ehrenberg. Solitary or colonial; individuals 

 with vase-like, hyaline, but sometimes, yellowish cellulose test, 

 drawn out at its base; elongated and attached to the base of test 

 with its attenuated posterior tip; 1-2 lateral chromatophores; 

 usually with a stigma; asexual reproduction by binary fission; one 

 of the daughter individuals leaving test as a swarmer, to form a new 

 one; in colonial forms daughter individuals remain attached to the 

 inner margin of aperture of parent tests and there secrete new tests; 

 encystment common; the spherical cysts possess a short process; 

 Ahlstrom (1937) studied variability of North American species and 

 found the organisms occur more commonly in alkaline regions than 

 elsewhere; fresh water. Numerous species. 



D. sertularia E. (Fig. 92,/). 30-44^ by 10-14^. 



D. divergens Imhof. 31-53)U long; great variation in different lo- 

 calities (Ahlstrom). 



Genus Hyalobryon Lauterborn. Solitary or colonial; individual 

 body structure similar to that of Dinobryon; lorica in some cases 

 tubular, and those of 'young individuals are attached to the exterior 

 of parent tests; fresh water. 



H. ramosum L. (Fig. 92, g). Lorica 50-70iu long by 5-9iu in diame- 

 ter; body up to 30m by 5ix; on vegetation in standing fresh water. 



Genus Stylopyxis Bolochonzew. Solitary; body located at bottom 

 of a delicate stalked lorica with a wide aperture; 2 lateral chromato- 

 phores; fresh water. 



S. mucicola B. (Fig. 92, h). Lorica 17-18m long; stalk about 33/^ 

 long; body 9-1 Iju long: fresh water. 



Family 4 Coccolithidae Lohmann 



The members of this family occur, with a few exceptions, in salt 

 water only; with perforate (tremalith) or imperforate (discolith) 

 discs, composed of calcium carbonate; 1-2 flagella; 2 yellowish 



