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HANDBOOK OF PROTOZOOLOGY 



Phalansterium digitatum Stein (Fig. 45, a) 

 17 microns long. 



The body about 



Family 2 Choanoflagellidae Stein 



Small flagellates, sometimes with the second flagellum which 

 serves for fixation of the body. A delicate collar surrounds the 

 flagellum. Ordinarily sedentary forms. If temporarily freed, 

 the organisms swim with the flagellum directed backward. 

 Often colonial. Free-living in fresh water. Holozoic on bacteria 

 or saprozoic. 



Fig. 45 a. Phalansterium digitatum. X400 (After Stein). 



b. Monosiga ovata. X600 (After Kent). 



c. M. robusta. X575 (After Stokes). 



d. Codosiga utriculus. X 1000 (After Stokes). 



Genus Monosiga Kent. Solitary; with a cytoplasmic collar. 

 Apparently without a shell. With or without stalk. Attached 

 to fresh or salt water vegetation. Several species. 



Monosiga ovata Kent (Fig. 45, b). About 10 to 15 microns 

 long. Salt water. 



Monosiga robusta Stokes (Fig. 45, c). About 13 microns 

 long. Fresh water. 



Genus Codonosiga Kent. Similar to Monosiga, but in- 

 dividuals are in a cluster-form at the end of a stalk which may 

 have branches. Fresh water. 



Codonosiga utriculus Stokes (Fig. 45, d). Attached to fresh 

 water plants. Body about 11 microns in length. 



Some of the other genera of the family are: 



Genus Desmarella Kent. Band-form colonies; simple or 

 branched. 



