PLASMODROMA, MASTIGOPHORA, CHRYSOMONADIDA 89 



abundantly in a water reservoir, the organism gives an offensive 

 odor to the water (Calkins). 



Genus Cyclonexis Stokes. Wheel-like colonial forms com- 

 posed of ten to twenty wedge-shaped individuals. Young colo- 

 nies are funnel-shaped. With two lateral chromatophores; no 

 stigma; reproduction and encystment unknown. 



Cyclonexis annularis Stokes (Fig. 30, m). Colony about 25 to 

 30 microns in diameter. In marshy water with Sphagnum. 



Genus Dinobryon Ehrenberg. Solitary or colonial. Individ- 

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

 test which is drawn out at its base. The delicate body is elon- 

 gated and attached to the base of the test with its attenuated 

 posterior tip. One or two lateral chromatophores; usually with 

 a stigma. Asexual reproduction by binary fission; one of the 

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

 new one. In colonial forms the daughter individuals remain 

 attached to the inner margin of the opening of the parent tests 

 and there secrete new tests. Encystment common ; the spherical 

 cysts possess a short process. 



Dinobryon sertularia Ehrenberg (Fig. 31, a). Fresh water. 



Genus Hyalobryon Lauterborn. Solitary or colonial. In- 

 dividual body structure is similar to that of Dinobryon. The 

 test in some cases, is tubular, and those of young individuals are 

 attached to the exterior of the parent tests. 



Hyalobryon ramosum Lauterborn (Fig. 31, b). Fresh water. 



Genus Stylopyxis Balachonzeff . Solitary. The body is lo- 

 cated at the bottom of a delicate stalked test with a wide aper- 

 ture. Two lateral chromatophores. 



Family 4 Coccolithophoridae Lohmann 



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

 salt water only. With perforate (tremalith) or imperforate (dis- 

 colith) discs, composed of calcium carbonate. One or two fla- 

 gella; two yellowish chromatophores; a single nucleus; oil drops 

 and leucosin. Nutrition holophytic. Examples: 



Pontosphaera haeckeli Lohmann (Fig. 31, c). 



Discosphaera tubifer Murray and Blackman (Fig. 31, d). 



