Peridiniacese 



59 



In Podolampas, in which there is no true transverse furrow, 'the missing girdle is 

 represented by a narrow band fused to the lower 

 ends of the precingular plates. On the surface 

 of this band, which is in the place along which 

 the transverse flagellum passes, is a very shallow 

 furrow' (Kofoid, '09 B). 



Crossing the transverse furrow on the 

 ventral side of the organism is a rather 

 more open longitudinal furrow, which is 

 best seen from an anterior or posterior 

 view of the organism. This furrow usually 

 extends but a little way into the apical 

 half of the cell, but it may reach to the 

 extreme apex, as in Gonyaulax apiculata 

 (Pen.) Entz. In' many cases it extends 

 only across the median part of the cell, 

 but it may sometimes be confined to the 

 antapical half, as in Peridinium Penardii 

 Lemm. The left margin of the furrow is 

 sometimes provided with a wing-like ex- 

 pansion, and if both margins are 'thus 

 extended the left one is the more strongly 

 developed. In some cases the furrow is so 

 expanded as to form a ventral area. 



B 



va 



Fig. 42. Ceratium tares Kofoid. A, 

 ventral view of empty cell. B, dorsal 



view of cell showing contents, x 400. 

 ch, chromatophores ; g, girdle; ??, nu- 

 cleus ; v, vacuole ; va, ventral area. 

 (After Kofoid.) 



STRUCTURE OF CELL-WALL. The firm 

 cell-wall is composed of definitely articu- 

 lated plates which consist largely of 

 cellulose and to a lesser extent of callose 

 and pectose (Mangin, '07). The whole 



outer covering thus forms a sort of exoskeleton which is divided by the 

 transverse furrow (or girdle) into an epivalve (or epitheca) and a hypovalve 

 (or hypotheca). These two halves, except in the Podolampina?, are separated 

 by the girdle, which may or may not be subdivided into several plates. 



It is, of course, the disposition of the transverse flagellum and its location 

 in a groove which in all the Peridiniacese is the primary cause of the division 

 of the cell into an apical half covered by the epivalve and an antapical half 

 covered by the hypovalve. 



Several proposals have been made with regard to the naming of the 

 plates composing the cell-wall. Stein ('83), Biitschli ('85), Schutt ('96), 

 Paulsen ('06), Faure-Fremiet ('08), and Kofoid ('09) have all put forward 

 systems of nomenclature, but that proposed by Kofoid has so many ad- 

 vantages over the other systems that it will without doubt be generally 



