230 ON THE BRITISH SPECIES OF ENTOMOSTHACA 



no fewer than eleven forms which, had been previously described 

 by himself or other authors as distinct species, and with a little 

 ingenuity it would be quite possible largely to increase this 

 number. 



I collected many years ago in Paston Lake, Northumberland, 

 numerous specimens of a Daphnia which I thought might be 

 referable to D. lacustris, Sars. Prof. Sars has kindly examined 

 some of these, and iu his opinion they do not belong to D. lactis- 

 iris, but to " one of the numerous varieties of D. longispina, in 

 this case one which forms a transition to D. hyalina.'''' It would 

 seem that D. galeata, Sars, together with D. longispina and its 

 varieties, are by far the most abundant of our lacustrine Daph- 

 nim, but that while D. galeata often descends into the abysses of 

 our deepest lakes, D. longispina seldom or never does so. 



The species to which 0. F. Miiller referred in his original 

 description of Daphnia longispina must remain doubtful ; but 

 the name is used by most authors with reference to a central 

 type, round which are clustered numerous long-spined and round- 

 headed varieties, which cannot be specifically separated by any 

 permanent or well-marked characters. It would seem, there- 

 fore, unwise to disturb this general agreement by futile conjec- 

 tures as to the species or variety which Miiller really had in 

 view. 



Yar. major, G. 0. Sars (fig. B). 



Daphnia longispina, var. major, Richard, Revision des Clado- 



ceres, p. 292, pi. 23, fig. 2. 



Head small, occupying one-fourth to one-fifth of the entire 

 length of the body ; rostrum acute, not much reflexed ; eye-spot 

 very minute ; dorsal and ventral margins of the valves boldly 

 arched, dorsal margin having a gentle depression behind the 

 head; spine long and slender, conspicuously bulging at its base 

 on the ventral aspect : post-abdomen bearing fourteen or fifteen 

 pre-anal spines. The limbs are of a deep brown colour (spirit- 

 specimens) and the post-abdominal teeth and unguis are simi- 

 liarly coloured. Shell very distinctly reticulated. In no stage 



