The Mastigophora 13' 



F, G); Cyanomonas Oltmanns (173, 202), with several blue-green chromatophores); 

 Rhodomonas Karsten (31, 202; Fig. 4. 15, C, E), with reddish-brown chromatophores. 

 Chromatophores are lacking in Chilomonas Ehrenberg (110; 202; Fig. 4. 15, L). 



Family 2. Cryptomonadidae. In these flagellates, the pharyngeal groove 

 is closed ventrally, through part or all of its length, to form a pouch. 

 The genus Cryptomonas Ehrenberg (110, 202; Fig. 4. 15, I-K) includes 

 chlorophyll-bearing forms; Cyathomonas Fromentel (110, 202), color- 



B 



a:) 



D 



Fig. 4. 16. A. Protochrysis phaeophycearum Pascher, xl500 

 (after P.). B. Cross-section of same. C. Nephroselmis olivacea Stein, 

 xl300 (after S.). D. Cross-section of jV. oUxmcea. 



less holozoic types in which the pharyngeal pouch is a functional gullet. 

 Family 3. Nephroselmidae. As compared with the other families, the 

 Nephroselmidae show a modification of the primitive cryptomonad or- 

 ganization. If the origin of the flagella is considered anterior, these 

 flagellates have become shortened along the anterior-posterior axis and 

 correspondingly elongated along the transverse axis. The result is a 

 more or less bean-shaped body, with the pharyngeal-groove and bases of 

 the flagella lying near the equatorial plane. The two genera, Nephro- 

 selmis Stein (202; Fig. 4. 16, C, D) and Protochrysis Pascher (202; Fig. 4. 

 16, A, B) differ in shape of the body in cross-section. 



Order 4. Dinoflagellida 



This order includes many living species and a variety of fossil 

 types (75). Most dinofiagellates are marine, forming an important part 

 of the plankton. Under conditions not yet fidly understood, the popu- 

 lations of certain dinofiagellates in localized areas may increase tre- 

 mendously, sometimes to densities above 5,000,000 per liter. The result 

 is discoloration of the water — "red water" or "red tide" — and lumi- 

 nescence at night, and occasionally the death of fish in large num- 

 bers (42). 



