440 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



diffuse, liaving the distal border imperfectly lobed and slender strands of granular pigment 

 distributed on the lens. It is elongated, 0.6 transdiameter in length, with a width of 0.5 its 

 own length. It is circular in cross-section and greenish blue at the distal end, changing to 

 yellow ochre towards the melanosome. Ventroposterior to the lens and partly embedding one 

 side of it is the melanosome. This is large, 0.3 transdiameter in length. It is composed of black 

 pigment with a red core. Streaming out from it are amoeboid strands of black granules, one 

 of which closely invests the right border of the lens, another passing over its dorsal face. 



The nucleus is large, elongate reniform, and occupies the central area of the body with its 

 major axis longitudinal. Rather coarse strands of chromatin curve around its major axis, about 

 fourteen on one face. Its length is 1.1 and its width 0.5 transdiameters. A small, pink club- 

 shaped pusule opens at the anterior and another at the posterior flagellar pore. 



The cytoplasm is rather coarsely granular with a few greenish oil droplets peripherally located 

 in the median and posterior regions. A large, blue-green food mass is found in the posterior 

 part near the ocellus. 



The color is bluisli green, diffused throughout the cytoplasm. The organism was enclosed 

 in a thin transparent cyst slightly larger than the body and conformable to its contour. An 

 unusual condition was noted in that a few bluish-green oil granules were present against the 

 inner surfaces of the cyst outside of the body. This species was found in both the encysted and 

 free state. ' The constrictions of girdle and sulcus were deeper in the encysted stage and the 

 ventral arching more pronounced in the free state. The cyst w^all was rather heavy and trans- 

 parent, adhered to the glass, and was rather closely applied in the two cysts obser\'ed. 



DiMEXSioxs. — Length, 60-64;i; transdiameter, 25-32.5/*; axes of nucleus, 36/^ 

 (18) and 15^ (10) ; length of lens, 19/^. 



The tniusual size of the nucleus figured was eAT-dentlv due to the approach 

 of division, the other forms seen having a much smaller ellipsoidal nucleus, as 

 may be seen from the measurements in parentheses. 



OccuERENCE. — Three individuals were taken July 23, 1917, 6 miles off La 

 Jolla, California, with a No. 25 silk net in a haul from 80 meters to the surface 

 and in a surface temperature of 20?8 C. 



CoMrAEisoxs. — Ponclietia atra is on the borderline between the two sub- 

 genera Pouchctia with diffuse ocellus and PouclicticUa with the concentrated 

 type. Its melanosome is only slightly lobed and its amoeboid streamers are 

 feebly developed. The lens is also elongate and slightly lobed and not fully 

 integrated by location into a t^Toieal axial relation to the melanosome. This 

 lack of complete concentration it shares with certain other species with pos- 

 terior ocellus such as P. albn, P. macidntu, and P. scliuetti, and with several 

 species with median ocellus such as P. maxima, P. poucheti, and P. piirjmrata. 

 The ocellus is farther posterior in P. afni than in any other species and exhibits 

 one of the later steps in the eA'olutionary integration of this organ towards the 

 concentrated tyjie. The ocellus in the free individual had a slightly more 

 anterior position and had more of an anterior direction of its optical axis, much 

 as in P. pur pu rat a. It is possible that the pressure of the food ball in the 

 individual figured (pi. 11, fig. 126) is responsible for the extreme posterior 

 position of its ocellus and for the discoloration of its lens. 



