KOFOID AND SWEZY : UNARMORED DINOPLAGELLATA • 479 



of a i^igmented sensory core is a prominent feature in the integrated type of 

 ocellus. The structural and morphological evidence is strong that the ocellus 

 of Enjtliropsis is functionally the most efficient optical organ among the Dino- 

 flagellata and the Protozoa as a whole. 



The "tentacle" (Hertwig, 1884), or dart ("dard," Faure-Freraiet, 1914), 

 or prod as we designate it (fig. RR, prod), is located rentrally in E. e.rtrndens 

 01" ventroposteriorly in E. minor and E. scarlatina, and posteriorly and axially 

 in the remaining species. It may be capitate, as in E. lab rum, E. pavillardi, and 

 E. extriidens, or lack distal enlargement as in the other species. It may have 

 a terminal stylet, as in E. Jiispida, E. extrndens, and E. corniita, or lack this, 

 as in other species. It has an axial, longitudinal, contractile group of fibers, the 

 I'etractor fibrillae (fig. RR, rctrac. fjb.), and a series of circular ones, the pro- 

 tractors. These antagonistic groups give to the organ an extraordinary degree 

 of mobility and render possible the extension of this organ to a length four times 

 that of the body. The operation of a Lamarckian factor of activity of this 

 organ in the origin of the ventral recess about its base and in the pushing of the 

 ocellus far anterior is suggested by the structural features of the genus. One 

 wlio has watched this organ in action has its potency strongly intimated to him. 



The occasional persistence of the longitudinal flagellum alongside this organ 

 precludes any possibility that it is a modified posterior longitudinal flagellum. 

 It appears rather to be a mobile margin of the sulcus specialized as an axial 

 organ, as foreshadowed in the prod of Proterythropsis and the mobile antapex 

 of Pouchetia and Cochlodinium. 



The paracingular lines which border the girdle on both sides in E. cornufa, 

 E. richardi, E. lahriim, and E. extrudens (fig. RR, pre. par. I., post. par. /.), and 

 may have been wholly or in part overlooked in the other species, are faint 

 modifications of the surface pellicle, or even slight modifications of the contours 

 which run parallel to the margins of the girdle throughout its whole course. 

 Their functional significance is wholly obscure and their homology ([uite prob- 

 lematical. The nearest approach to anything like them in the Diuoflagellata 

 are the precingular and postcingular series of plates in the thecate forms. But 

 there can lie no possibility of the origin of such rows of plates from these para- 

 cingular areas. The similarity of the relationship of the paracingular lines on 

 the one hand and the rows of plates on the other to the girdle suggests tlie func- 

 tion of the latter in influencing, if not originating, such organs. 



The presence of huge melanosomes and of the red pigment in the plasma 

 of E. scarlatina and in the sensory core of the ocellus of most species, and in 

 the entire pigment mass of E. agilis, estalilishes the predominance of the red 

 end of the spectral colors in this genus, thus continuing the same relationship 

 of these pigment colors to specialization which was detected in the genus 

 Pouchetia. 



No chroinatophores are present. No food lialls have been detected, Init it is 

 ]>n)1)abk' that the species are holozoic, as is Pouchetia. 



