OF THE ENGLISH LAKE DISTRICT. 441 
" subspecies,"' " varieties/' and " Eonns " have been described. I do not 
propose to discuss the question of the systematic arrangement of these 
Daphnias, but it seems to me that the enlargement of the significance of the 
name JJ. longispina in this sense has serious disadvantages, and that the 
suggestion of Langhans that a new name, D. variabilis, should be introduced 
to include the whole series of these variable Daphnias might with advantage 
be adopted. The question can, however, hardly be regarded as finally 
settled, and, for the present, it is more satisfactory to accept Lilljeborg's 
longispina, hyalina, and cucullata, whilst fully recognising that the three are 
united by transitional forms. 
All the limnetic Daphnias of the lakes belong to the " species " liyalina 
with its " subspecies " galeata and lacustris. Beck has recorded the occur- 
rence of D. cucullata (under the name Hyalodaphnia berolinensis), but this 
species has been seen in the district by no one else, and it is probable, that 
he was mistaken. Daplinia is absent altogether from Wastwater and 
Ennerdale Water, and apparently also normally from Bassenthwaite. There 
are none from the latter lake either in Dr. Poarsall's collections or my own, 
and Mr. Scourfield informs me that he also failed to find it there. On the 
other hand. Miss Pratt records both D. pule.v and D. longispina as occurring 
in April 1898, so that apparently some species occurs there at times. As 
Bassenthwaite receives the overflow from Derwentwater which contains an 
abundance of Daplmia, it is very remarkable that the same form should not 
establish itself in Basseiithwaite. 
The distribution of the different forms of Daplinia in the district seems to 
bear little or no relation to the drainage system. While Buttermere and 
Orummock, which were originally united into one lake, both contain tlie 
typical D. hyalina, which occurs in these lakes only, the Dapknia of 
Esthwaite is quite different from that of Windermere, into which Esthwaite 
drains, and the same form, D. galeata, inhabits Windermere and Coniston, 
which are not connected in any way. 
Daphnia hyalina s. str., in Buttermere and Orummock. 
In the form from these two lakes the front of the head is usually very 
nearly straight or slightly concave (text-fig. 3, A) : but it is very variable, 
and may occasionallj^be distinctly convex as in D. pellucida. In a collection 
made on Aug. 27, 1920, several specimens were seen with the front of the 
form shown in text-fig. 3, B. An exactly similar variety is illustrated by 
Lilljeborg (1900, pi. xv. fig. 4) as "forma cestivalis rnonstrosa." It is 
characteristic of the Orummock Daphnias that the shell-spine forms a con- 
siderable angle with the body axis — from 20°-40". Although I regard this 
form of Daphnia as properly referable to D. hyalina s. str., Lilljeborg, in 
some respects the population is transitional on the one hand to D. lacustris 
and on the other to D. pellucida. 
LINN. JOUEN. — ZOOLOGY, VOL. XXXV. 32 
