418 
MR. R. GURNEY ON THE CRUSTACEAN PLANKTON 
bill, tbe former should be specially studied with a view to seeing if, as is 
probably the case, the ;>lankton of the deep and the shallow basin differs in 
composition. 
Table 3. — Composition of the Plankton. 
Cold-water Species. 
Eiirytlierm Species. 
Warui-waler Species. 
Wastwater . . . . 
2 
3 
— 
Eunerdale 
3 
2 
— 
Orumiiiock . . . . 
3 
2 
— 
Coniaton 
2 
4 
— 
Wiudevmere . . . . 
2 
4 
3 
Ullswatei- 
3 
3 
— 
Hawes Water . . 
3 
3 
1 
Derweiitwatei- . 
1 
5 
3 
Bassenthwaite . 
- 
4 
3 
E.sthwaite 
1 
4 
5 
The JSorthern J^lemeitt in the JHlankton. 
The general character of the plankton is very distinct from the Central 
European and Baltic types and resembles that of Scotland. Characteristic 
of it is the absence of Daphnias of the cucullata-grov.]) and of Bosmina 
longirostris from all the lakes except Esthwaite and Grasmere, and of 
Ceriodaphnia from all but Windermere and Esthwaite. 
The general abundance of Bosmina obtiisirostris in itself marks the 
plankton as of the northern type, but the following species are also 
characteristic of northern or arctic lakes : — 
Holopediimi yibberum. 
Daphnia hyalina s. str. 
Bythotrephes longimanus 
Polyphemus pediculus. 
Biajytomus laticeps. 
Limnocalanus macinirus. 
Cyclops abyssorum. 
Biaphanosoma brachyuriim niay be looked upon as belonging to a southern, 
warm-water, genus, but it is itself so widely distributed throughout Europe, 
in cold as well as in warm waters, that little importance can be attached to 
