430 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



turns, as in P. purpnrcscens (pi. 8, fig. 84) and P. fusus (fig. PP, 1), these 

 terminal loops of tlie sulcus are lacking and the ends of the sulcus have Kttle 

 or no torsion, thus resembling CocJilodinium. 



The length and torsion of the sulcus are intimately correlated with the 

 length, proportions, and constriction of the body, and the terminal loops tend 

 to increase the asymmetry of the species of this genus as compared with more 

 sjanmetrical species of Cocklodinium (cf. figs. GG and 00). 



The presence of an antapical loop encircling the antapex heloiv the point of 

 emergence of the posterior longitudinal flagellum accentuates the as}anmetry 

 of the antapical region (see P. maculata, pi. 11, fig. 119), and provides the basis 

 for a progressive mobility of this region within Pouclietia, which renders this 

 territory very difficult to examine and portray adequately and correctly. It 

 also affords the earlier stages in the evolution of the remarkably active and 

 extra ordinay prod, or tentacle, of Protcrijtliropsis and Erijtlirop-sis. 



It seems probable that the apical loop performs a like function for the apex, 

 which in Erythropsis is invaded by the anterior end of the sulcus and is some- 

 what labile. In P. violescens, P. jiino, and P. atra (figs. 00, 1, 3 ; PP, 5) modi- 

 fications of the apical region are brought about by this apical loop of the sulcus. 



The ocellus in Pouclietia has all stages in the integrative process of com- 

 bining scattered pigment spherules into a compact mass enveloping the base 

 of the lens, and in a correlated combination of separate hyaline spheres into a 

 sj)heroidal laminate lens. 



This process is clearly one of integration. The evidence for this conclusion 

 lies in the fact that those species (subgenus Pouclietia) with the diffuse non- 

 integrated \j^e of ocellus, such as P. alha (fig. PP, 8), P. poucheti (fig. PP, 4), 

 P. schiietti (fig. PP, 10), and P. purpurata (fig. PP, 3), are not highly special- 

 ized in other structural features. They are nearer to Gumnodinium and Cocli- 

 lodinium than are the species with the integrated ocellus. They have less torsion 

 in the gii'dle and sulcus, and both P. alba and P. poucheti are almost colorless 

 (pi. 11, figs. 121, 125), being lightly tinged with yellow and blue respectively, 

 while P. schuetti and P. purpurata with a more concentrated type of ocellus 

 reach the red end of the spectrum. P. fusus is yellow, has the Cocldodinium 

 t^iie of torsion, without terminal loops in the sulcus, and its ocellus lias a unique 

 ringlike melanosome binding together a bipolar lens. 



The group of species (subgenus PouchetieUa) with more highly integrated 

 lens and melanosome also has within it various stages in the later phases of the 

 integrative process. In fact the distinctions between the two groups are not 

 clearly defined. The highest stage of integration results in a spheroidal lens 

 with concentric laminae, with one face buried in a black pigment mass or 

 melanosome which is also spheroidal or hemispheriodal and contains within its 

 center, in contact with the surface of the lens, a highly colored sensory ( ?) core. 

 Such ocelli are to be found in the highly specialized species such as P. juno. 

 P. violescens, P. maxima, and P. striata (fig. 00). They are usually median 

 in position and have their axes horizontal or 45° from the horizontal and directed 



