162 ROTATUKIA 



We have uhtained a single specimen of this form from sample L 86a, and I)elieve it to lie 

 sufficiently distinct to merit recognition; we therefore propose the name C. wiszniewskii n. n. 



In addition to these forms, two other very close allies of the species have l>een described. 



Dii^lcna rok-ocicola Zavadovski (1916), for which the author proposed, should it prove 

 to be but a variety, the unnecessary alternative D. catcUina parasitica (ncc Plciirotrocha para- 

 sitica Jennings = C. parasitica Ilarring and Myers), is a form living in colonies of J'oli'ox. 

 We have unfortunately been unable to obtain the original description, but according to 

 Harring and Myers the figures that accompany it do not show "any differences that luight 

 be considered of specific value. Some physiological dissimilarities are described, the most 

 striking one being the parasitism of the animal in Wilvox colonies." Hutchinson, Pickford 

 and Schuurman (1932) record from inside colonies of Vol^-ox in two shallow fresh-water 

 pans a form determined by them as C. catclliiia. Re-e.xamination of some of this material 

 shows that it represents a form of Cephaloddla in some respects intermediate between C. 

 catellitui and C. ri'iszniewskii, resembling tlie former in the narrow l)ase of the toe in proportion 

 to its length, and the latter on the other hand in the concavity f)f its anterior margin, though 

 this is more marked in the volvocicolous form. 



Recently de Beauchamp (1932) has described a very large form with a short curved toe 

 from the plankton of Lake Elmenteita in Kenya. This form he regards as a species Cepha- 

 lodella elmenteita because the preserved specimens on which it was based lacked the character- 

 istic eye-spots of C. catclliiia. We have, however, been unable to oliserve eye-spots in any 

 specimens of forms of C. catellina preserved in formalin and then cleared in glycerine, and 

 therefore believe the difference to be illusionary. Moreover, in the marginal sample from the 

 alkaline Pangur Tso we have o!)tained a form of C. catcUina which has toes \vhich though 

 straight show a basal constriction as in C. elmenteita. Our Pangur Tso form, therefore, 

 seems in one of its characters to be transitional to de Beauchamp's species. For this Pangur 

 Tso form with its basally constricted toe, -wt propose the name f. ahlstromi, Mr. Ahlstrom 

 who observed some speciiuens of the form in a tube of Brachioniis material having pointed 

 out to us the desirability of examining the form more closely. Mr. Ahlstrom believes the 

 Pangur Tso form to have a shorter and in preserved specimens more plicated head than 

 is normal, but we are not convinced that these differences are not entirely due to presers^a- 

 tion. Intergrades l^etween f. catellina and f. ahlstromi appear to occur, for of throe s])eci- 

 mens of catellina from Los Angeles, California (det. Myers), kindly lent us for study by the 

 American Museum of Natural History, two specimens have a typical toe, and the third a 

 definitely constricted toe as in ahlstromi, the toe in this specimen is however slightly longer 

 (body 120/i, toe 2U'.) than in the latter form, in this resemlding the specimens of f. catellina 

 with which it occurred. 



The various forms of C. catellina may be tabulated as follows : 

 C. catellina (Miiller). Length 110-135^, to.' 20-25^, about one-fifth or one-sixth of the 

 total length, long, narrow, anterior margin practically straight, widest at the practically 

 unconstricted base. (Figttre 1 c.) 



f. ahlstromi n. Length 95-112/u, toe 15-18'/, just under one-sixth nf the total length. 

 long, narrow, slightly concave both anteriorly and posteriorly, straight, basally ctmstrictcd 

 and widest distinctly distally to base. (Figure Id.) 



