KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 405 



is clvib-shaped in Pavillardin trnturuUfcra, 0.75 transdiameter in length and 0.12 in greatest 

 diameter, which is in the inidtile half of the length. At its proximal end it is constricted to half 

 its middle diameter and contracts distally to a blunt point. Throughout its entire length except 

 at the ti]i and base it is suffused with a brilliant, burnt orange brown color which is quite 

 uniforndy translucent and shows no internal differentiation. It is habitually carried in an 

 oblique position about 30° ventrally from the axis, slightly arched with the concave side ventral. 



The surface of the body is covereil with a thin pellicle with a nai-row clear zone beneath 

 except at the poles where this is obliterated. A few minute yellowish i)latysomes are scattered 

 somewhat irregidarly near tlie surface and several linear ones mark out (faintly) several striae 

 on the right side of the longitudinal furrow on the epicene. 



The cell contents consist of the nucleus located slightly in front of the middle of the body. 

 This is large, 0.66 transdiameter in diameter in dorsal or ventral view and 0.5 in lateral view, 

 due to the cup-shaped depression on the posteroventral face. It is double-contoured, with a 

 heavy membrane and is packed full of extraordinarily thick chromatin threads slightly modu- 

 lated. Sixteen of these strands, possibl.y not all distinct, are to be counted on the dorsal face. 

 Tliere- is evidence of polarization of the strands. Running posteriorly from the flagellar pore 

 at the proximal end of the girdle is a short canal leading towards a slender conical pusule, 

 probably collapsed, but not clearly connected with the canal. The dorsal surface has a suffused 

 rosy tone from certain radial aeciunulations of reddish substance located peripherally. A cluster 

 of minute red spheres is lodged near the antapex. There is no trace of a lens or pigment mass 

 such as are found in the eyespot of Pouchetia. No distinct chromatophores could be detected, 

 though the body as a whole has a pale yellowish tone. Neither rhabdosomes nor oil drops Avere 

 noted in the individuals under observation. The brilliant brown tentacle makes the animal a 

 conspicuous object in the mieroplankton. Luminiscence not tested. 



Dimensions. — Leugtli, 58/^; transdiameter at girdle, 27/^, at widest part of 

 hypoeone, 31^^; length of tentacle below antapex, 19^; axis of nucleus, 19/^ and 

 IS/'. 



Behavior. — Cytoh'sis ensues in ten to fifteen minutes under illiunination 

 in tlie microscope with ordinary daylight, the tentacle persisting entire nearly 

 as long as the nucleus but neither surviving more than a minute after cytolysis 

 sets in. The behavior of the motile organism is much like that of Protodinifcr 

 described above. The tentacle is somewhat more moljile, being raised frequently 

 to a right angle to the axis or even above this and jerked back with a couvidsive 

 jerk. Eotation in the anticlockwise direction is frequent with a gliding anterior 

 movement which must be due to the posteriorly directed current in the ventral 

 furrow. The body is somewhat metabolic. In one individual tmder observjition 

 small protu])erances of the body were thrust out on the dorsal and postero- 

 dorsal part of the h}^)ocone and quickly retracted, without innnediate patho- 

 logical consequences. 



OccuKRENCE. — This was taken July 2, 1917, with a No. 12 silk net, 6 miles 

 off La Jolla, California, in a haul 60 meters to the surface and in a surfar-e 

 temperature of 20-5 C. On Jidy 20 it was again noted in a haul 6 miles off- 

 shore from 80 meters to the surface, and on July 25, 11 miles offshore, and on 

 July 27, 4 miles offshore in hauls from 80 meters to the surface and surface 

 temperature of 21-9 C It was present in hauls made in the previous smnmer, 

 and was also observed by the senior author in ]»lankton from a red-water out- 

 Ijreak off La Jolla in July, 1907. 



