444 MR. R. aURNEY ON THE CRUSTACEAN PLANKTON 
Burckliarilt's D. lujaUna forma lucernensu from the Lake of Lucerne is 
evidentljr the same variety. In one individual from Esthwaite the dorsal 
projection of the head is denticulate as figui-ed bj Burckhardt for his forma 
jiuussica. 
Derwentwater. 
The Daplmias from Derwentwater rather closely resemble I>. ligalina s. str., 
but should, I think, rather be included in _D. lacustris by reason of the 
concave front and rather higher head. The dorsal angle characteristic of 
the form from Esthwaite and Hawes Water is occasionally, but very rarely, 
seen in Derwentwater. 
Daphnia galeata, Sars. 
The typical form of D. galeata occurs throughout the year in Ooniston, 
Windermere, and LFllswater, being most abundaut in the former. Although 
Dr. Pearsall's samples cover every season in the year, I have not found 
ephippial females in any of them, so that the species appears to be acyclic. 
The same appears to be the case with the D. lacustris of Esthwaite, Hawes 
Water, and Derwentwater, but in Crnmmock and Buttermere there is a 
distinct sexual phase in D. liyalina in October, though, even here, the species 
persists through the winter. 
Daphnia — Seasonal Variation. 
The material at my disposal does not admit of any positive statement with 
regard to seasonal variation of form, but such variation is very slight if it 
occurs at all. With regard to D. galeata, in which it could most easily be 
detected, I have found on the one hand crests equally as high in winter as in 
summer, and individuals with a quite round head in July and August. I 
have no doubt that a small variation of bead-form, and of size of liody, could 
be shown statistically with sufficient material, but the variation is certainly 
not so pronounced as to be appreciable to the eye. 
In this respect also the plankton of these lakes differs markedly from the 
Danish and Central European lakes, and approaches the northern type. 
BOSMINA OBTUSIROSTRIS, Sars. 
The identity of the northern races of B. coregoni with those occurring in 
the alpine lakes is now established, and, according to lilihe, the united species 
should be known under the name of B. coreffoni-longispina. As, however, 
the name B. longispina has generally been used in a more restricted sense, 
and is so used by Lilljeborg, and as the name B. obtusirostris has been 
universally used for the northern forms with short umcro, I prefer to retain 
it in Lilljeborg's sense. 
In the Lake District this species occurs, often in great abundance, in nearly 
all the lakes. Its apparent absence From Buttermere may be dite to the fact 
that the collections were made from the shore only ; but, although a single 
