KOFOID AND SWEZY: UNAEMORED DINOPLAGELLATA 17 



had evidently l)eeii digested before it came under our observation, the remaining 

 theea presenting the appearance of being crushed together and of massing near 

 the posterior end of the body, preparatory to being ejected on the release of 

 the organism from its cyst. Pcridiuiidu of this t}7De are large organisms and 

 the half shell still intact has a length equal to about 0.5 of the total length of 

 the body of the Fouchetia, showing that the iBgested organism was about equal 

 in size to the marauder which had captured it. The length of the intercin- 

 gular area in this species is about 0.5 of the total length of the body, hence its 

 distension must have been enormous to enable it to grapple successfully with 

 a food mass of this size. 



In its simplest condition the sulcus is a shallow furrow joining the ends of 

 the girdle, but this stage is relatively rare, as it usually presents various modi- 

 fications. The anterior and intercingular portions of the sulcus usually present 

 few variations of structural details beyond the apical loop. Its posterior ex- 

 tension may sink into the body, forming a deep excavation at the antapex, or 

 it may even bifurcate the entire posterior half of the body, as in Gymnodinium 

 hifurcafiiw (fig. AA, 3). In Amphidluiion the sides are often drawn out into 

 flaps which are thro^^Ti across the furrow and cover the opposite border (fig. 

 21, 5). It may also function iu the production of pseudopodia (Zaeharias, 

 1899) , as in Gym nodinium zachariasi (fig. BB, 3) , in the tentacle of Protodinifer 

 fpl. 7, fig. 74), in the ventroposterior process of ProferytJiropsis (pi. 11, fig. 

 123), and in the prod of Erythropsis (pi. 12). 



Its extreme mobility is undoubtedly correlated with its function as the 

 mouth of the organism. The process of food-taking in the dinoflagellates is 

 still a mystery. Many of the forms observed in the cytoplasm are those of active 

 organisms and the means by which they are caught and held until the engulfing 

 protoplasm receives them are xjuzzling in the extreme. The great mobility of 

 the lips of the sulcus probably offers a solution to the puzzle. Saville-Kent 

 (1880-82) observed Gy)nnodiniiuit marinum actively devouring smaller monads 

 in the culture with it, engulfing them at this region without the formation of 

 l^seudopodia. Critical evidence as to the exact nature of this activity in other 

 members of the grouj) is ahnost entirely lacking. 



