176 THE MASTIGOPHORA 



Sub-Family SYRACOSPHAERINAE. Pontosphaera (Fig. 6, D), Scypho- 

 sphaera (Fig. 6, A), Syracosphaera, and Calyptrosphaera all described by 

 Lohmann. 



Sub-Family COCCOLITHOPHORINAE, Lohmann. Coccolithopora, Loh. ; 

 Umbilicosphaera, Loh. ; Discosphaera, Haeck. (Fig. 6, F) ; Rhabdosphaera, 

 Haeck. 



C. CHRYSOMONADIXA MEMBRANATA. 



Mallomonas, Perty ; Synura, Ehrenberg ; Syncrypta, Ehrenberg (Fig. 

 5 (4)) ; Uroglena, Ehrenberg (Fig. 5 (5)) ; Microglena, Ehrenberg ; Hymeno- 

 monas, Stein. 



TRIBE 3. CRYPTOMONADINA, Biitschli. 



Coloured or colourless forms with one to three green chromatophores 

 or none. Nutrition is never holozoic and the product of metabolism is 

 starch, as in green Algae and in Dinoflagellata. The anterior end is 

 more or less obliquely truncate, usually with a deep frontal infundibulum l 

 like a peristome, from the side or bottom of which the two flagella arise. 



Cryptomonas (holophytic), Ehrenberg ; Cyathomonas, Fromentel ; and 

 Chilomonas (saprophytic), Ehrenberg. 



In Cryptomonas the colour of the chromatophores varies from green to 

 brown and yellow ; two are dorsal and one ventral. Cyathomonas possesses 

 no chloroplasts. 



Closely related to the Cryptomonadina are the Phaeocapsaceae, contain- 

 ing the genera Phaeococcus, Borzi ; Phaeosphaera, West ; and Stichogloea, 

 Chodat. In these forms a large number of non-flagellate cells form a 

 mucilaginous investment ; but as the asexual reproduction takes place 

 principally during this phase of life, they are more usually regarded as 

 algae. The same may be said of the genus Hydrurus, Ag., in which the 

 cells are enclosed in a tough cylindrical mucilaginous envelope. 



SUB-CLASS II. CHOANOFLAGELLATA, Saville Kent. 



The Choanoflagellata are frequently regarded as constituting 

 a subdivision of the Protomastigina, a proceeding which is in 

 accordance with their affinities, though such is the singularity 

 of their form that it seems quite as appropriate to preserve their 

 independence as to merge them into a larger group. There are 

 no permanently free-swimming species, all are either sessile or 

 pedunculate, solitary or colonial. They can, however, quit their 

 .attachment temporarily and swim about with the collar directed 

 backwards. The collar may be defined as a special development 

 of the peristome surrounding the single flagellum which acts as a 

 pulsellum in locomotion. The collar is a contractile protoplasmic 

 process comparable in some respects to an undulating membrane. 



The organism feeds by means of vacuolar ingestion, the food 



1 Flagellar fundus. See also under Dinoflagellata, p. 187. 



