KOFOID AND SWEZY: UNARMORED DINOPLAGELLATA 345 



in Gyrodininm, as in G. niaculafion (pi. 6, fig. 62). One species, Cochlodinium 

 gcminatum (fig. HH, 1), contains yello^Y-oclll'e cliromatophores. 



Nearly all the colors of the spectrum are to be found within this genus, 

 with a preponderance of yellow and yellow ochre. At the red end of the spec- 

 trmn are C. archimedes, C. constrictum, C. rosaceum (pi. 8, fig. 85), and C. 

 miuiatxni (pi. 10, fig. 107), with aster purple in C. radiatu))} (pi. 6, fig. 67). A 

 faint reddish tone is found in G. scintiUans (pi. 10, fig. 113) and C. augustum 

 (pi. 5, fig. 53). Three species are green in color, C. convolutnm (pi. 10, fig. 115), 

 G. faurei (pi. 2, fig. 25), and G. darissirmim (pi. 5, fig. 60), the latter obscm^ed 

 by pink peripheral vacuoles. Two species have a bluish tint, G. vinctum (pi. 2, 

 fig. 15) and G. pulchdhim (pi. 2, fig. 21), and the remainder are yellow and 

 yellow ochre in color, varying in a few species to a yellow green. 



All the species in the genus GocJilodiniuni are probably holozoic in nutrition, 

 with the possible exception of the one species containing chromatophores, G. 

 gennnatum. In the other species, with few exceptions, the cytoplasm contains 

 evidences of holozoic nutrition in the form of food masses, refractive rodlets, 

 vacuoles and oil globules, the accumulated ijroducts of metabolism. There is 

 some slight evidence in G. vinctum (fig. HH, 3) of selective feeding. 



Cyst formation is common throughout the genus, the cyst consisting of a 

 thin-walled hyaline membrane. Occasionally double cysts are formed, one 

 within the other. In some species binary fission takes place within the cyst, 

 as in G. pulchellum (figs. HH, 14, 16). In other eases cyst formation is evi- 

 dently correlated with the ingestion of food balls and serves as a digestion cyst, 

 as in G. clarissinium (fig. GO, 2) and G. cavatum (fig. HH, 10). 



Distribution 



The genus Gocltlodiiiium as a whole is somewhat more restricted in its range 

 than either Gymnodinium or Gyrodiniiim. It has no fresh-water represent- 

 atives. All the species thus far described have come from warm temperate 

 waters, with none from the polar or tropical seas. Possible exceptions to this 

 may be found in the species described by Schiitt (1895), since he mifortunately 

 omitted to mention the localities from which his species were ol)tained. They 

 were presumably from the Bay of Naples or the warm Atlantic fi-om the col- 

 lection of the Plankton Expedition, and make up half the number of the pre- 

 viously described species. His species are G. constrictum, G. gcminatum, G. 

 pirum, G. sclmetti- (= Gymnodinium helix, Schiitt, 1895, in part), and G. stran- 

 gulatum. Two more species described by Pouehet (1883, 1887) complete the 

 record for the Atlantic. These are G. archimedes and G. helix. G. pinim has 

 also been recorded from the ^Mediterranean at Naples, Italy, by Entz, Jr. (1909). 



The only CocltJodinium thus far recorded from the Baltic is G. pellicidum, 

 near Kiel, Germany, by Lohmann (1908), A single species has been figured 

 from Yokohama Harbor, Japan, G. catenatum, by Okamura (1916). Three 

 species have been recorded from Plymouth Sound, England, by Miss Lebour 

 (1917&). 



