50 THE INVERTEBRATA 



Order CHRYSOMONADINA 



Yellow, brown, or colourless phytomastigina ; without starch reserves, 

 but usually with leucosin and oil ; without gullet or transverse groove ; 

 often amoeboid. 



The genera briefly mentioned under this and the following orders 

 illustrate the range of variety within the group. 



Chrysamoeba (Fig. 38 A, A^). One flagellum; two yellow chromato- 

 phores; no skeleton. Egg-shaped when swimming, but on the sub- 

 stratum becomes amoeboid and may lose flagellum. Ingests food by 

 pseudopodia. In fresh waters. 



Ochromonas (Fig. 38 B). As Chrysamoeba^ but with two unequal 

 flagella; and usually one chromatophore. 



Dinobryon (Fig. 38 C). Two unequal flagella; two yellow chro- 

 matophores. Secretes a flask-shaped house, which in some species 

 adheres to those of other individuals to form a pseudocolony. In fresh 

 waters. 



Hydrurus (Fig. 38D-D2). One flagellum; one chromatophore. 

 Passes most of its life in the resting stage, which by division forms 

 a plant-like growth (see p. 47). In fresh waters. 



Rhizochrysis. Flagella normally lacking; one chromatophore; body 

 naked and permanently amoeboid. 



Leucochrysis . As Rhizochrysis, but colourless. 



Silicoflagellata (or Silicoflagellidae) . One flagellum; numerous 

 yellow chromatophores ; a lattice-work case of hollow, siliceous bars. 

 Marine, planktonic, e.g. Distephanus (Fig. 38 F). 



Coccolithophoridae . One or two equal flagella; two chromatophores 

 (sometimes green) ; a case composed of calcareous plates {coccoliths) 

 or rods (rhabdoliths) enclosing the body. Marine, planktonic, e.g. 

 Syracosphaera (Fig. 38 E). 



Order CRYPTOMONADINA 



Green, yellow, brown, or colourless phytomastigina; with starch (and 

 occasionally also oil) reserves ; with gullet or with longitudinal groove, 

 without transverse groove; very rarely amoeboid. 



Many of the yellow members of this group live in the resting stage 

 as symbionts in other organisms.^ 



Cryptomonas (Fig. 39 A). Two flagella; two chromatophores, 

 usually green; a gullet. Marine and in fresh waters. 



^ Owing to certain features of their nucleus and its mode of division these 

 symbionts have been held to be related to the Dinoflagellata. Their other 

 features, however, are those of the Cryptomonadina. 



