66 



Peridiniede 



Plate ('06) as a fixed band running round the transverse furrow and with 

 both ends passing into the flagellar pore. The inner fixed border of the 

 band is thickened, whereas the outer border is very delicate, and the move- 

 ment consists of wave-like undulations of this delicate free edge. Lemmer- 

 mann (10) also states that he has on several occasions observed a similar 

 band-like transverse flagellum in the larger species of Peridinium, such as 

 P. topes, P. Willei, etc. 



The locomotion of some species of Ceratium and other Peridiniace* 

 appears to be intermittent, but Glenodinium will often remain continuously 



Fig. 48. Peridinium Steinii Jorg. subsp. mediterraneum Kofoid. A, dorsal view of cell showing 

 the large antapical spines; B, optical section through body of cell; a.v., accessory vacuole; 

 c', c", canals of pusules opening at the flagellar pore which in this species is in a very 

 posterior position; c.p., collecting pusulej I, leucoplasts; s.p., sack pusule. x 570 (after 

 Kofoid). 



active for many hours. Some of the Peridiniacese possess trichocyst-like 

 structures in the peripheral part of their protoplasts, either near the flagellar 

 pore or near the apical pore. 



In some forms, and particularly in Peridinium Steinii, there is a well- 

 marked ' pusule apparatus,' which was first described by Schiitt ('92 ; '95). 

 This consists of certain peculiar vacuoles in the protoplast, and it is 

 doubtful if they are present in more than a few forms. In Peridinium 

 Steinii (fig. 48) there is a large bilobed ' sack pusule ' which opens by 

 a short funnel-shaped canal leading to the flagellar pore. On the ventral 



within range of these reagents their movements immediately slow down and in many cases the 

 undulating transverse flagellum is thrown right out of the transverse furrow. 



