104 HA NDBOOK F PRO TOZOOLOG Y 



Family 4 Noctilucidae Kent 



The somewhat contractile tentacle arises from the sulcal 

 area and extends posteriorly. Formerly this group had been 

 included in the Cystoflagellata. Studies by recent investigators, 

 particularly Kofoid, show their affinities with the present sub- 

 order. Holozoic. Marine. 



Genus Noctiluca Suriray. Body spherical, bilaterally sym- 

 metrical. Peristome marks the median line of the body. A 

 cytostome at the bottom of peristome. With a distinct tentacle. 

 The cytoplasm is much vacuolated, and cytoplasmic strands 

 connect the central mass with the periphery. Colorless or blue- 

 green, sometimes tinged with yellow coloration in the center. 

 Swarmers are formed by budding, and each possesses one 

 flagellum, girdle, and tentacle. Widely distributed in salt water. 

 One species. 



Noctiluca scintillans (Macartney) (= N. miliaris Suriray) 

 (Fig. 35, e,f). Usually 500 to 1000 microns in diameter, with 

 the extremes of 200 microns and 2mm. 



Family 5 Gymnodiniidae Kofoid 



Naked form with simple but distinct furrows. Several genera 

 in fresh or marine water 



Genus Gymnodinium Stein. Ordinarily naked, subcircular; 

 numerous discoid chromatophores vari-colored (yellow to deep 

 brown, green, or blue) or sometimes absent. Stigma occasionally 

 present. Longitudinal fission in active form; cyst with a mu- 

 cilaginous or firm envelope. Marine, brackish, or fresh water. 



Gymnodinium agile Kofoid and Swezy (Fig. 35, g). About 

 28 microns long. In sandy beaches. 



Genus Hemidinium Stein. Body oval; girdle about half a 

 turn. 



Hemidinium nasutum Stein (Fig. 35, h). Oval, assy metri- 

 cal. Sulcus on hypocone. Chromatophores yellow or brown. 

 Nucleus posterior. Transverse fission. 24 to 28 microns long. 

 Fresh or brackish water. 



Genus Amphidinium Claparede and Lachmann. Variable 

 form ; epicone small, girdle near the anterior end ; sulcus straight 

 on hypocone or also on part of epicone. With or without 



