DINOFLAGELLATA 251 



body with a red, brown or yellow core, located at left of sulcus; 

 sulcus expands posteriorly into ventro-posterior tentacle; salt water. 

 Several species. 



E. cornuta (Schiitt) (Fig. 107, h). 104/x long; off California coast 

 (Kofoid and Swezy). 



Family 4 Noctilucidae Kent 



Contractile tentacle arises from sulcal area and extends poste- 

 riorly; a flagellum; this group has formerly been included in the 

 Cystoflagellata; studies by recent investigators, particularly by 

 Kofoid, show its affinity with the present suborder ; ho lozoic; saltwater. 



Genus Noctiluca Suriray. Spherical, bilaterally symmetrical; peri- 

 stome marks the median line of body; cytostome at the bottom of 

 peristome; with a conspicuous tentacle; cytoplasm greatly vacuo- 

 lated, and cytoplasmic strands connect the central mass with peri- 

 phery; specific gravity is less than that of sea water, due to the pre- 

 sence of an osmotically active substance with a lower specific gravity 

 than sodium chloride, which appears to be ammonium chloride 

 (Goethard and Heinsius); peripheral granules luminescent (p. 100); 

 cytoplasm colorless or blue-green; sometimes tinged with j^ellow 

 coloration in center; swarmers formed by budding, and each posses- 

 ses one flagellum, annulus, and tentacle; widely distributed in salt 

 w^ater; ho lozoic. One species. 



A^. scintillans (Macartney) (A^. miliaris S.) (Fig. 107, i, j). Usu- 

 ally 500-1000/i in diameter, with extremes of 200;u and 3 mm. 

 Gross (1934) observed that complete fusion of two swarmers (isoga- 

 metes) results in cyst formation from which trophozoites develop. 

 Acid content of the body fluid is said to be about pH 3. 



Genus Pavillardia Kofoid and SwezJ^ Annulus and sulcus similar 

 to those of Gyimiodinium; longitudinal flagellum absent; stout 

 finger-like mobile tentacle directed posteriori}^; salt water. One 

 species. 



P. tentaculifera K. and S. 58ju by 27 /x; pale yellow; off California. 



Family 5 Gymnodiniidae Kofoid 



Naked forms with simple but distinct 1/2-4 turns of annulus; 

 with or without chromatophores; fresh or salt water. 



Genus Gymnodinium Stein. Pellicle delicate; subcircular; bi- 

 laterally symmetrical; numerous discoid chromatophores vari- 

 colored (yellow to deep brown, green, or blue) or sometimes absent; 

 stigma present in few; many with mucilaginous envelope; salt, 

 brackish, or fresh water. Numerous species. 



