28 PEOTOZOA 



Key to the genera of H eteromonadidae : 



d Solitary forms 1- MONAS 



o 2 Colonial forms. 



6 X Common stalk branched once or twice ; on Cyclops . . 2. CEPHALOTHAMNIUM 

 6 2 Common stalk much branched 3. ANTHOPHYSA 



1. MONAS Ehrenberg. Body spherical or ovate, occasionally fast- 

 ened by a thread-like stalk ; 2 flagella: 3 species; in fresh water. 



Fig. 26 Fig. 27 Fig. 28 



Fig. 26 Monas elongata (Conn). Fig. 27 Cephalothamnium ccespitosum (Conn). 

 Fig. 28 Monosiga ovata (Calkins). 



M. elongata (Stokes) (Fig. 26). Body elongate; hinder end tapers 

 to form stalk; length .01 mm. 



2. CEPHALOTHAMNIUM Stein. Body ovate, with one long and one 

 short flagellum; animals colonial and sessile, the stalk branching two 

 or three times and several individuals being grouped at the end of each 

 branch : 2 species ; in fresh water, often on Cyclops. 



C. csespitosum (Kent) (Fig. 27). Body with obliquely truncated 

 anterior end; length of individual .02 mm. 



3. ANTHOPHYSA Bory. Body as in above; stalk much branched: 

 1 species; in fresh water. 



A. vegetans (0. F. Miiller). Length of individual .03 mm., of 

 colony .4 mm. 



ORDER 3. CHOANOFLAGELLIDA. 



Collar flagellates. Collar-like ridge surrounding the base of the 

 single flagellum which is at the hinder end of the body when the animal 

 swims, instead of at the forward end as in other flagellates; in some 

 forms 2 collars are present, one over the other: 2 families. 



FAMILY CRASPEDOMONADIDAE. 



Either solitary or colonial and either free-swimming or sessile and 

 often enclosed in a cup or a gelatinous envelope: 4 genera. 

 Key to the genera of Craspedomonadidae : 



Oi Shell wanting ; animals sessile or stalked. 



&! Stalk shorter than body or wanting 1. MONOSIGA 



Z> 2 Stalk long, with many individuals at the end 2. CODONOSIGA 



6 3 Stalk long, branched at end 3. CODONOCLADIUM 



o. Shell present 4. SALPINGOSCA 



