256 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Gymnodinium simplex (Lobmanu) Kofoid and Swezy 

 Text figure BB, 8 



Protodinium simphjc Lohinaim (1908), pp. 264, 265, pi. 17, fig. 17; (1911), pp. 23, 30, 31, 



fig. 12. 

 P. simplex, Schiller (1911), p. 31. 

 P. simplex, Ostenfeld (1913), p. 339. 



Di.\Gxosis. — This is a minute species with broadly ellipsoidal body, its length 

 1.53 transdiameters ; girdle median, a closed circle; sulcus absent (1) ; yellow, 

 leaf like chromatophores. Length, 20/*. Baltic Sea near Kiel, Germany, tlu'ough- 

 out the year. 



Description. — The body is broadly ellipsoidal with broad apices, circular in cross-section, its 

 length 1.53 transdiameters at the widest jjart. The girdle is poorly defined in Lohmann's figure 

 (our text figure BB, 8), but seems to be median in position, dividing the body into two subequal 

 parts, both subhemispherical in shape, with broad, rounded apices. His figure further lacks 

 flagella and pores as well as any indication of a sulcus. The latter structures he notes as absent. 



The nucleus is a relatively large body centrally located and filled with chrouiatin granules. 

 Its diameter is about 0.6 transdiameter of the body in length. Yellow, leaflike chromatophores 

 are arranged in the periphery of the cell. These vary from four to many in number. 



Dimensions. — Length, lO-20/i; transdiameter, 13m; diameter of nucleus, 8m. 



Occurrence. — Described by Lohmann (1908) from the Baltic Sea near Kiel, 

 Germany, where it occurred throughout the year, sparingly in the winter and 

 reaching its maxiinmn in July. 



Synonymy. — This species was described by Lohmann as Protodinium 

 simplex, thus creating for it a new genus Avithotit, however, a full statement of 

 his reasons for so doing. The lack of a definite sulcus cannot well be used as 

 a generic distinction, since this structure, as well as the girdle, is sometimes 

 lacking in Lohmann's figures of other species, as well as in those of many 

 earlier biologists. It possesses only the characters of the girdle, hypocone, and 

 epicone, which identify it with the group of minute Gijhinodiuiiim, and we there- 

 fore place it in that genus, discarding Lohmann's new genus, Protodi)iii())i, 

 pending a full reexamination of these details. In the event that there is no 

 trace of the sulcus prior to cytolysis, the genus Protodinium might well stand 

 and be transferred to the Protodiuiferidae. Our reluctance to place it there 

 now is based on our experience with living, naked dinoflagellates in crowded 

 plankton collections, such as those with which Lohmann evidently worked. The 

 rounding up of the body under these conditions tends to obliterate the girdle 

 and sulcus, and this may have been the case with tlie individuals on which 

 Lohmann's figures and description are based. 



