344 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



The constriction of tlie body is closely correlated with the length of the 

 girdle and sulcus. In forms with the shorter girdle, as 1.5 turns in C. cavatum 

 (fig. HH, 10), the l^ody is nearly always greatly constricted on the morpholog- 

 ically ventral face, Avith a resulting ventral excavation of the ])ody, as in C. 

 cavatum and C. helix (fig. HH, 8), or with the ventral surface thrown into 

 rounded lobes, as in C. viuctum (fig. HH, 3) and C. conspiration (fig. GG-, 10), 

 with the dorsal side convex in both cases. The most aberrant form in this 

 respect is C. distortinn (fig. HH, 9). With the lengthening of the girdle the 

 constrictions extend around the body, as in C. lehourae (fig. HH, 7), the number 

 of lolies increasing with the turns of the girdle and sulcus \uitil the maximum 

 in the genus is reached in G. angustiim (fig. HH, 15). 



The borders of the sulcus are not protiiberant, yet they are apparently 

 capable of great distension, as the sulcal area evidently forms the region for 

 tlie ingestion of food. Comparatively huge food bodies are frequently noted 

 in the cytoplasm, as in C. rosaceum (pi. 8, fig. 85), and the ingestion of these 

 must place great strain on the sulcal region, particularly in forms like C. 

 august uni. 



The nucleus is usually located near the posterocentral part of the body. 

 Its chromatin contents are always arranged in the beaded, moniliform threads 

 characteristic of the Dinoflagellata generally. Two species only, C. miniatum 

 (fig. GG, 6) and C. stixmyuJatuni Schiitt, present a perinuclear membrane of 

 the iy^G occasionally found in Gyroclinium. 



The c;\i:oplasmic organization in the genus CocliJodinium never reaches the 

 relatively high degree of ditferentiation sometimes foiind in Gjjmnodinium and 

 Gjjrodinium. The nearest approach to ectoplasmic differentiation is seen in 

 C. cJarissimum (pi. 5, fig. 60), with its supei-ficial vacuolated layer. The 

 peripheral zone of short rodlets so prominent in Gyrodinium is rarely met 

 with in this genus, C. citron alone presenting it (fig. HH, 12). 



The surface of the body in this genus is relatively free from striae, and, 

 unlike the genus Pouchctia, striae are here associated with primitive or more 

 generalized species with one exception, C. distortum (fig. HH, 9). Only three 

 other species have striae, C. volutum (fig. GG, 1), C. pirum (fig. GG, 3), and 

 C. mineatum (fig. GG, 6). 



The color of the c}i:oplasm in the genus Cochlodinium is varied, often bril- 

 liant and changealjle in tone. The color may be diffused throughout, as in C. 

 rosaceum (pi. 8, fig. 85), G. citron (pi. 7, fig. 79), and G. conspiratum (pi. 3, 

 fig. 29), or it may be massed in ckunps or irregular bodies. In C. radiatum 

 (pi. 6, fig. 67) the aster-purple pigment is found in irregular, leaflike masses 

 scattered through the periphery. The yellow ochre of G. atromacuJatum (pi. 7, 

 fig. 71 ) is scattered through the peripheral zone while the melanin is aggregated 

 into ellipsoidal masses along the girdle. 



In G. distortum (pi. 7, fig. 78) the ochraceous-orange color is distributed 

 along the surface striae in globules of A-arying sizes, recalling similar conditions 



