114 . MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



OccTTERENCE. — Described from four individuals taken in a plankton haul 

 made witli a No. 12 silk net from forty fathoms, six miles off La Jolla, California, 

 in the California Current, July 2, 1917, in surface temperature of 21-95 C. 

 It was observed also on July 20, 6 miles offshore, July 25, 11 miles offshore, 

 July 27, 4 miles offshore, and August 13, 0.75 mile offshore, in surface temper- 

 ature varying from 21-95 to 22-45. It was also taken on July 12 and 20, 1906, 

 in surface hauls off La Jolla made between 5 and 6 a.m. 



Activities. — The tentacle is habitually held in a somewhat rigid position, 

 directed anteriorly, with a slight dorsal curvature. In moribund individuals 

 it is gently waved to and fro in a short arc intermittently. When in a more 

 active condition the flagellmn is energetically raised to the horizontal plane 

 and thrust back in a quick stroke which drives the animal backward with a 

 sudden dart. 



The behavior of the animal imder the cover glass is generally, however, of 

 a someAvhat different nature. It moves with little rotation in a clockwise spiral 

 anteriorly for short periods intermittently, with an occasional dart posteriorly. 

 This posterior movement is an unusual one among dinoflagellates, and there 

 seems to be no other motor organ than the tentacle to accomplish it. The sup- 

 pression of the function of rotation may be due to the imperfect girdle and the 

 varying position of the transverse flagellmn. 



CoMTARisoxs. — This genus is unique among the tentacle-bearing dinoflagel- 

 lates in the anterior position of the girdle, and in the exceedingly rudimentary 

 stage of development of this characteristic feature of the order. In Enjtliropsis 

 agilis Hertwig the girdle is as well developed as in Pouclietia, and the tentacle 

 or prod is relatively very much larger. In addition this genus is provided with 

 a prominent lens and pigment mass. In PavUlardia tentacidifera the tentacle 

 is quite similar in size and shape to that in Protodinifer, but it is colored a 

 brilliant brown, as is the pigment in Pouclietia rosea, and the girdle and longi- 

 tudinal furrow are of the Gyrodinium tj'pe. In Gymnodinium pseudonoctiluca 

 the girdle is complete and located far anterior and the tentacle is proportion- 

 ately longer than in Protodinifer. 



From these comparisons it is evident that the genus is not closely affiliated 

 with any of the other tentaeulate dinoflagellates. It resembles Hemidiniiun 

 and Noctiluca in the incompleteness of the girdle, but the former is an isolated 

 fresh-water genus in which little speciation has occurred, while this one feature 

 exhausts its resemblances to Noctiluca. The simplicity of structure places 

 Protodinifer at the lowest level of the tentacle-bearing dinoflagellates. The 

 anterior position of the flagellar pore and the very slight differentiation of the 

 two flagella, the proportions of the body and the coloration are strongly sug- 

 gestive of a relationship to Prorocentnim. It lacks, however, all trace of a 

 theca and must l)e regarded as an athecate representative of the Diniferidae 

 of primitive type from which the Adiniferidae are an offshoot. The feebly 

 developed sulcus and girdle are indicative of tendencies which, if accentuated, 



