152 C. ISHIKAWA. 



The dorsal side of the tail shows four prominences as in the female, 

 but these are all very small, and arc of nearly the same si?:-e. The 

 lower edge of the tail is a little more concave than in the female, but 

 the denticles, spines etc. are quite similar to those of the other sex. 

 The apical claw is perhaps a little larger comparatively and slightly 

 more curved. 



The colour of the animal is much lighter than in the female. 



Systenmtic position of the species. — The present species is most 

 closely allied to European D. pulex or to D. pennata, to both of which the 

 ge]ieral shape of the body and the shell, and the external structures of 

 the various parts of the body of the parthenogenetic female are closely 

 alike. The descriptions of the females of these species as given by B. 

 Hellich * or by Eylmann f may fairly pass foi' the above described 

 parthenogenetic female of D. Whitmani. The only points of difference 

 by which the present species differ from its European allies are the 

 presence of a fewer number of anal denticles, the greater number of the 

 basal sets of teeth of the apical claw, and the dorsal row of spinules 

 extending farther forwards. The number of the anal deiiticles is hov;^- 

 ever, as described above, not quite constant in our species, and the 

 dorsal row of spinules although not constantly found in the partheno- 

 genetic female, is present in the gamogenetic one in nearly the same 

 extent as in the two European species, leaving only the shape and the 

 number of the proximal set of teeth of the apical claw, so that I was at 

 first rather inclined to think our Daphnia to l)e a local variety of D. 

 pulex or of D, pennata, but the shape and the structure of the male is 

 quite different from the males of both of them. Its much larger eyes, 

 the larger size of its first pair of antenua, as well as its dorsal processes 

 of the tail, distinguish it, among other characters, at once ft'om these 

 species. 



Observations : — D. Whitmani was first observed by myself in an 

 iron tank containing rainy water in the garden of the Imperial 



* Bohuslav Hellich I.e. p. 20, 27. 

 t E. Eylmanu I.e. p. 13, 15 and 16. 



