138 The Mastigophora 



The flagellate stages of many species fall within the range, 10-200[ji,. 

 However, certain parasitic types grow to diameters of 600-700[jl, while 

 Noctiluca scintillans sometimes measures 1.0-1.5 mm. A girdle and a 

 sulcus are characteristic of flagellate stages (Fig. 4. 17, A). The girdle 

 (or annulus) is a groove which usually encircles the body in a descending, 

 or sometimes in an ascending, left-hand spiral, although the two ends 

 may meet in the same plane. In extreme cases, the girdle may trace more 

 than one complete spiral, or it may be rudimentary as in Protonocfiliiai 



Fig. 4. 17. A. Gymnodinlum dorsum Kofoid and Swezy; pusules opening 

 into flagellar pores; x940 (after K. & S.). B. Cochliodinium lebourae Kofoid 

 and Swezy, spirally twisted sulcus; x525 (after K. & S.). C. Amphidiniopsis 

 kofoidi Woloszynska, dorsal view showing intercalary bands; x630 (after 

 W.). D. Gymnodinium racemosus .Cofoid and Swezy, showing chromato- 

 phores; x475 (after K. & S.). E. Protonoctiluca (Protoditiifer) tentaculatum 

 (K. & S.), showing tentacle arising from sulcus; x700 approx. (after Kofoid 

 and Swezy). F. Cross-section of apical horn, Ceratium hirundinella; diagram- 

 matic (after Entz). G. Erythropsis extrudens Kofoid and Swezy, showing 

 prod and outline of ocellus; x450 (after K. & S.). Key: b, intercalary band; 

 e, epicone; //?, flagellar pore; g, girdle; /;, hypocone; //, longitudinal flagel- 

 lum; o, ocellus; p, pusule; pr, prod; 5, sulcus; t, transverse flagellum; te, 

 tentacle. 



