KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 



343 



In the simpler, more generalized species of CocModinium we find a type of 

 girdle only slightly removed from that of Gijrodiniiun, as in C. scintiUans (fig. 

 GG, 11), where the girdle is 1.5 turns in length, with a torsion of 0.5 in the 

 sulcus. The greatest development of the girdle is found in C. augustum (fig. 

 HH, 15), and C. imlchcllmn (fig. HH, 16), the former with four turns, the 

 latter with nearly three turns aroimd the ])ody, with a corresponding develop- 

 ment of the sulcus. Intermediate stages between these two extremes are 

 common. 



The torsion of the body, as shown / °^\ 



in the sulcus, is confined almost exclu- L ,-/-~^°\ 



sively to the interciugular region with, *"^'^ / 'TTk^ 1 



rarely, an apical or antapical loop added A r/ft(V^°n \ 



thereto. The striking exceptions are ^„^ r'r^sSl^'A 



C. clarissimum and C. atromaculotum , 7 '^ v^^^^'V --ir.fi. 



the former with an apical, the latter ^"'^ 17^^^^^^'v^^^^^ 



with an antapical loop. In this respect i r^^^--^K^'^^'^ ^^- 



the genus differs from Pouchetia, where A't^^^^'^^^^SkNo ' ^>*^'- 



the apical or antapical regions mav s^r. r^5:^4^^^^ f^NX ' / ^'' 



show as much if not more torsion than ^ ^vVm^^^^^^^^^ ^'' 



the interciugular area. -1^-0 — l^I^^t^^ix" ^"^' 



"With the lengthening of the girdle ,'' \(°X^^^^V^''''*T '"^' 



and the resulting torsion of the body a ^^-'^-^^ \<f^°^jC^l gir 



profound change takes place in the ori- ""-.^ ^^^CxC / 



entation of the organism. Considering " \v^^^^ post. p. 



the longitudinal plane passing through x'^V^ 



the flagellar pores as the dorsoventral xL/T — long.fi. 



plane of the body, the two pores both I 



open on the ventral face, as in Am phi- Fig. ff. cochindinium auomacuiatum sp. uov. 



dininm, Chimnodhuum, and nearlv all Abbreviations: a«t p anterior flagellar pore; .j,,;., 



■' _ _ • epicone; gir., girdle; hyp., hypooone; long, ft., longi- 



the species of Gfjrodinmm. With the tmUnal flagellum; n., nucleus; pifir., pigment; po.s«. p., 



lengthening of the girdle in some species fo^te™^ p^^; suic, sulcus; u. fi., transverse flagei- 



'^ p. '^ ,-, T, n. ■ luni; rac, vacuoles. X 500. 



or Gyrodinmm and m Cochlodinmm 



the posterior pore is pushed around the body and, while the median longitu- 

 dinal plane lies midway between them, the moi"phological median dorsoventral 

 plane undergoes torsion with the body. Thus in all the simpler species of 

 CocModinium the anterior pore opens on the right, the posterior pore on the 

 left face of the figure, as in C. vinctum (fig. HH, 3). The posterior pore may 

 thus be carried completely around the body and regain its position in tlie same 

 median i)lane with the anterior pore, as in C. radiataw (fig. GG, 12) with two 

 tui-ns of the girdle and in C. augnstum (fig. HH, 15) with four turns of the 

 girdle. This position, however, in which both pores come to lie together in the 

 median plane, is secondai-ily acquired, and the morphological dorsoventral 

 plane has imdergone a torsion of two or four full turns respectively to accom- 

 plisli the results. 



