ENTOMOSTKACA OF MINNESOTA. 203 



Daphnia cucnllata Sars. 

 Kurz (vitrea). 



Very like the above, but the margin of head is not straight below, 

 is, however, extremely variable and ends in a sharp angle. The eye 

 lies nearly midway between the heart and the end of the head and 

 near the lower margin. The two anterior processes of the abdomen 

 are united for most of their length. Anal teeth five to seven. Claw 

 ciliate. The fiagellum of the male antenna is about as long as the ter- 

 minal setsB. 



J), apicata Kurz seems to be a large variety lacking the sharp spine 

 of the head. In the main it agrees quite well. Although the post- 

 abdomen is broader than figured by Mueller, the number of teeth cor- 

 responds with Sars' description. 

 Length 0.95 to 1.11 mm. 



* Daphnia kalbergeusis Schoedler. 



Plates XXVII, Figs. 1-3; LIII Figs. 5-8. 



Schoedler (coederstrasmii, and berolinensis); Forbes (retrocurva). 



Eather delicate species of moderate size, inhabitants of clear and 

 deep waters. Form oval, with a long nearly straight spine springing 

 from near the middle of the posterior margin. Head very large and 

 produced into an enormous helmet-like crest, which projects cepha- 

 lad and may be somewhat or greatly curved dorsad. The size of the 

 crest and its form are very variable even in the same gathering. Eye 

 small, with few lenses, distant from the ventral margin, macula want- 

 ing. Antennte weak. Post-abdomen narrow, with from six to twelve 

 anal teeth; claws weakly ciliated. Abdominal processes discrete. 



As above stated, the close association of forms in the same gather- 

 ing ranging from D. vitrea to the extreme of D. retrocurva seems to 

 forbid their separation, even varietally. The case of D. vitrea is most 

 open to doubt. The chief differences seem to lie in the small number 

 (4) of anal teeth and the fusion of the two anal processes. A young 

 specimen from Lake Minnetonka had but four large teeth and two 

 inconspicuous ones and the anal processes were less distinct than in 

 older individuals. All transitions could be found. We agree with 

 Hellich that this, at most, is a depauperate variety of J>. Icalhergensis. 

 There seems to be absolutely no good reason for separating D. ceder- 

 stroemii or D. retrocurva, as the differences are largely a matter of age 

 and freedom to develop typically. 



P. E. Mueller gives the following measurements for D. Jmlbergevsis: 

 Head 0.9 to 1,0 mm., body 1.0 to 1.1 mm., spine 0.7 to 0.75 mm. 



