68 LABORATORY STUDIES IN ZOOLOGY 



The matching of organisms with figures is not to be recommended 

 as a general method, but in an introductory study of micro- 

 organisms it facihtates the gaining of famiHarity with the different 

 types. 



If needed, further explanation in the use of the key will be 

 given by the instructor. 



Key for the Identification of Protozoans Most Commonly Found 

 IN Fresh-water Cultures 



Should forms be found which do not appear to be included in 

 this key, they need not be identified. 



A. Locomotor organs not cilia. 



B. Flagella as organs of locomotion Class Madigophora 



C. Solitary (not colonial). 



D. With test formed in plates; one anterior horn and one to three 



posterior horns; groove encircling body Ceratium 



DD. Without test. 



E. Colorless; i.e., without green, yellow, or brown chromato- 

 phores. 

 V. Body truncate or concave at anterior end, slightly flattened; 



two flagella Chilomonas 



FF. Body not truncate at anterior end. 



G. Body elongate, wider at posterior end; two flagella, one 



long and heavy, one short and fine Astasia 



GG. Body oval, flattened, not wider at posterior end, and very 

 flexible, gullet present with rodlike organ back of mouth ; 



one flagellum Peranema 



EE. With green chromatophores. 

 F. Body not spindle shaped. 



G. Body spherical, or eliptical in form with one largo cup- 

 shaped chromatophore and stigma (eyespot); two 



flagella Chlamydomonas 



GG. Body round or pear shaped, not symmetrical, with 



caudal process; one flagellum Phacus 



FF. Body spindle shaped; gullet present; single flagellum; 



stigma present Euglena 



CC. Indi^^duals associated in colonies. 



D. With yellowish brown chromatophores. 

 E. Colon}' spheroidal. 



F. Individuals embedded on surface of a gelatinous mass; two 



yellow chromatophores Uroglena 



FF. Individuals not embedded in gelatinous mass and loosely 



joined; two flagella Symira 



EE. Colony arboroid; each individual resting in a cellulose cup; 

 one long, one short flagellum; the cup of each individual 

 attached within the cup preceding it Dinobryon 



