1 84 



THE MASTIGOPHORA 



The genera thus fall into two groups : 



A. Annulus and sulcus simple, at right angles to one another, decus- 

 sating at one point, from which the two flagella take their origin. 



Gymnodinium, Stein. Freshwater and marine. Hemidinium, Stein 

 (Fig. 10 (1)). Freshwater. Amphidinium, Clap, and Lach. 



FIO. 10. 



1, Diagram of Hemidinium, one of the Dinoflagellata; 71, nucleus; /, flagellum of the 

 transverse groove ; h, flagellum of the vertical groove. 2, diagram of Oxyrrhis, one of the 

 Heteromastigoda (to compare with the preceding); n, nucleus; g, the deep fossa or pit in 

 which the two flagella are affixed ; t, the origin of the flagellum, which corresponds with that of 

 transverse groove of Dinoflagellata. 3, Glenodinium einctum, Ehrb., one of the Peridiniaceae ; 

 a, amyloid granules ; 6, eye-spot ; c, chromatophores ; d, flagellum of the transverse groove ; 

 , flagellum of the vertical groove ; v, vacuole. 4, the same seen from the hinder pole. 5, 

 cuticle of Histioneis cymbalaria, iStein, from the Atlantic ; i, ventral process ; k, cuticular 

 collar ; I, posterior process. 6, the same seen from the dorsal surface ; m, cephalic funnel 

 (epitheca). 7, cuticle of Amphisolenin globifera, Stein, from the Atlantic, seen from the left 

 side ; m, epitheca ; o, the fundus from which the sulcus proceeds to the sub-terminal annulus ; 

 p, pharynx ; q, the shrunken protoplasm. 8, cuticle of Ornithocereus magnificus, Stein, from 

 the Atlantic ; m, m', the epitheca ; r, r', the two large ribs of the cuticular collar ; s, the two 

 rows of cuticular teeth. 9, cuticle of Ceratocorys horrida, Stein, from the Southern Ocean ; 

 p, p', borders of the annulus expanded into a rim ; w, x, y, plumose spines of the left margin 

 of the sulcus. (After Lankester and various authors.) 



