DINOFLAGELLATA 321 



C. asymmetricum C. (Fig. 129, p). 68-80^ by about 10/x; brackish 

 water (Conrad, 1926). 



Family 6 Elastodiniidae Kofoid and Swezy 



All parasitic in or on plants and animals; in colony forming genera, 

 there occur trophocyte (Chatton) by which organism is attached to 

 host and more or less numerous gonocytes (Chatton). Taxonomy 

 (Chatton, 1920; Reichenow, 1930). 



Genus BJastodinium Chatton. In the gut of copepods; spindle- 

 shaped, arched, ends attenuated; envelope (not cellulose) often with 

 2 spiral rows of bristles; young forms binucleate; when present, 

 chromatophores in yellowish brown network; swarmers similar to 

 those of Gymnodinium; in salt water. Many species. 



B. spinulosum C. (Fig. 130, a). About 235/* by 33-39/z; swarmers 

 5-10ju; in Palacalanus parvus, Clausocalanus arcuicornis and C. 

 furcatus. 



Genus Oodinium Chatton. Spherical or pyriform; with a short 

 stalk; nucleus large; often with yellowish pigment; on Salpa, Anne- 

 lida, Siphonophora, marine fishes, etc. 



0. poucheti (Lemmermann) (Fig. 130, b, c). Fully grown indivi- 

 duals up to 170/x long; bright yellow ochre; mature forms become 

 detached and free, dividing into numerous gymnodinium-like 

 swarmers; on the tunicate. Oikopleura dioica. 



O. ocellatum Brown (Fig. 131, a, b). Attached to the gill filaments of 

 marine fish by means of cytoplasmic processes; oval in form; 12m by 

 10m to 104m by 80m, average 60m by 50m; nucleus spherical; many 

 chromatophores and starch grains; a stigma. When grown, the or- 

 ganism drops off the gill and becomes enlarged to as much as 150m 

 in diameter. Soon the cytoplasmic processes and the broad flagel- 

 lum are retracted and the aperture of shell closes by secretion of 

 cellulose substance. The body divides up to 128 cells, which become 

 flagellated and each divides once more. These flagellates, 12/x by 8m, 

 reach the gills of fish and become attached (Brown, 1931; Nigrelli, 

 1936). 



O. limneticum Jacobs (Fig. 131, c, d). Pyriform; 12ju by 7.5m to 

 20ju by 13/x; light green chromatophores variable in size and shape; 

 no stigma; without flagella; filopodia straight or branched; the or- 

 ganism grows into about 60m long in three days at 25°C; observed 

 maximum, 96m by 80m; starch becomes abundant; fission takes place 

 in cyst; flagellate forms measure about 15m long; ectoparasitic on the 

 integument of freshwater fishes in aquaria (Jacobs, 1946). 



