STATE GEOLOGIST. 239 



DAPHNIA Sp? 



(Plate X, figs. 15-16). 



From a cold marsh a gathering in June, 1882, contained several fe. 

 males like that represented by fig. 16. They were far from being 

 abundant, however, and the pool contained no other Daphnia showing 

 that it was unfavorable to the growth of these animals. 



These females differ from D. pulex chiefly in their small size, dVo cm.) 

 being the smallest Daphnia seen with an evidently mature appearance. 

 The caudal spine is sickle-shaped; post-abdomen as in pulex; antennae 

 short; the animal beautifully clear and varigated by the brilliant con- 

 tents of ovary, eggs and intestine. I hesitate to regard it as a destinct 

 species. 



Figure 15 represents a single specimen of Daphnia found with the 

 above which was somewhat injured during its moult. This resembles 

 D. apicata, Kurz, and D. pellucida, Mliller, and is perhaps the male of 

 the species represented by fig. 16. Our knowledge of the variations 

 induced by "environment is yet too meager to draw up definitions of 

 species with certainty from a single, gathering, but these forms are pe- 

 culiarly interesting. 



See also the accompanying figure, (fig. 1,). These forms merit closer 

 study. 



