326 PROTOZOOLOGY 



Family 1 Peridiniidae Kent 



Shell composed of numerous plates; annulus usually at equator, 

 covered by a plate known as cingulum; variously sculptured and 

 finely perforated plates vary in shape and number among different 

 species; in many species certain plates drawn out into various proc- 

 esses, varying greatly in different seasons and localities even among 

 one and the same species; these processes seem to retard descending 

 movement of organisms from upper to lower level in water when 

 flagellar activity ceases; chromatophores numerous small platelets, 

 yellow or green; some deep-sea forms without chromatophores; chain 

 formation in some forms; mostly surface and pelagic inhabitants in 

 fresh or salt water. 



Genus Peridinium Ehrenberg. Subspherical to ovoid; reniform in 

 cross-section; annulus slightly spiral with projecting rims; hypotheca 

 often with short horns and epitheca drawn out; colorless, green, or 

 brown; stigma usually present; cysts spherical; salt or fresh water. 

 Numerous species. Species and variation (Bohm, 1933; Diwald, 

 1939); Chromatophore and pyrenoid (Geitler, 1926). 



P. tabulation Claparede and Lachmann (Fig. 132, c). 48/t by 44/i; 

 fresh water. 



P. diver gens (E.) (Fig. 132, d). About 45/i in diameter; yellowish, 

 salt water. 



Genus Ceratium Schrank. Body flattened; with one anterior and 

 1-4 posterior horn-like processes; often large; chromatophores yel- 

 low, brown, or greenish; color variation conspicuous; fission is said 

 to take place at night and in the early morning; fresh or salt water. 

 Numerous species; specific identification is difficult due to a great 

 variation (p. 223). Biology and morphology (Entz, 1927); encyst- 

 ment (Entz, 1925). 



C. hirundinella (Muller) (Figs. 94; 132, e). 1 apical and 2-3 antap- 

 ical horns; seasonal and geographical variations (p. 223); chain- 

 formation frequent; 95-700/x long; fresh and salt water. Numerous 

 varieties. Reproduction (Entz, 1921, 1931; Hall, 1925a; Borgert, 

 1935); holozoic nutrition (Hofeneder, 1930). 



C. longipes (Bailey) (Fig. 132, /). About 210/i by 51-57 M ; salt 

 water. 



C. tripos (Muller) (Fig. 132,0). About 225/i by 75/x; salt water. Wailes 

 (1928) observed var. atlantica in British Columbia; Martin (1929) 

 in Barnegat Inlet, New Jersey. Nuclear division (Schneider, 1924). 



C.fusus (Ehrenberg) (Fig. 132, h). 300-600/x by 15-30/*; salt water; 

 widely distributed; British Columbia (Wailes), New Jersey (Martin), 

 etc. 



