424 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Di:\rENSioxs. — Length, 95-100/^ ; transdiameter, 60-63m ; diameter of nucleus, 

 31m; length of ocellus, 30/^; of nematocysts, 14—22/^. 



Activities. — It is very active, rotating on its axis in anticlockwise direction 

 Tvith occasional brief rcA-ersals, and circling, under the cover glass, in clockwise 

 circles. As it slows down the rotation ceases and the circles decrease in size 

 until their diameter is only one to two times the length of the body. No dis- 

 charge of the nematocysts has been noted either before or after cytolysis. 



OccuEEExcE. — A number of individuals were seen in the plankton at La 

 Jolla, California, in July and August, 1917, but not recorded. Two were re- 

 corded from the hauls of a No. 25 silk net from 80 meters to the surface, 6 and 

 4 miles off La Jolla on July 20 and 27 respectively in surface temperatures of 

 20?5 C and 21?4 C respectively. A third was taken in a surface haul off the 

 pier at the laboratory on August 4 in surface temperature of 21°5 C. 



Dogiel (1906) records it as xevy abundant in surface plankton at times at 

 Naples, Italy, during his investigations from May to the middle of July. ]\Iiss 

 Lebour reports it as coumion in water samples from Ph-mouth Sound, England, 

 in May and June in both free and encysted condition. These samples were 

 taken 2.5 miles offshore from the surface and from 5 and 7 fathoms. 



CoMPAEisoNS. — The most striking difference between Dogiel 's P. armata 

 and our material of this species is in size. Our material has a length of 95fi 

 and TOO/*, as determined by the measurement of two different individuals. His 

 magnification is given as 850. If true, his organism was only one-half the size 

 of ours, or 50/*. A comparison of length, transdiameter, diameter of nucleus, 

 lengths of nematocysts and of ocellus of his figure with our own reveals the fact 

 that all these dimensions are but one-half those in oiu' records, on the basis of 

 his recorded magnification of 850. However, he also uses a magnification of 



425 for certain other figures. If this magnification is applied to his figure the 

 dimensions of the axis and organs noted above coincide almost exactly with 

 those of our specimens. We regard this as an indication that the magnification 

 given by him is i^robably an oversight and that the discrepancy in size may 

 not exist. Miss Lebour (1917?>) gives neither figure nor dimensions of her 

 material. In proportions, girdle, sulcus, color, and numlier and arrangement 

 of nematocj^sts our specunens agree closely with Dogiel's, except for the fact 

 that his figure has reversed symmetry with the torsion and girdle running in 

 the opposite direction to the normal and usual one. This appears to be due 

 to error in his having drawm the structures of the lower surface upon the iipper 

 one. No case of critically determined, reversed s^Tmnetry is known to us in 

 the Dinoflagellata, and this error of reversal of s,^Tnmetry is one easily made 

 in our experience. 



This species shares with Neniatodininin parfition the possession of nema- 

 tocysts which have not been found elsewhere in the family. They are of the 

 same t}'pe and size as in Poli/krikos, although somewhat larger (10-15/*) in 

 this species than in N. parfifmu (6/* to 8/*). 



