OF THE ENGLISH LAKE DISTRICT. 43? 
relative length o£ the innermost seta in C. abyssorum is perhaps the easiest 
character by which the species may be separated, but Prof. Sars has 
ennmerated a number of details wherein the species differ. It is to be hoped 
that Prof. Sars' limitation of these species will be followed, since it is most 
probable that they will be found to have different life-cycies and different 
habitats and distribution. The general' adoption of Schmeil's definition of 
C. strenuus has made comparison of statements with regard to these questions 
unreliable and indeed valueless. So far as published information goes, it 
seems that ('. abyssorum is confined to northern lakes, and is absent from 
Swiss lakes, where apparently a form resembling C. scutifer takes its place. 
The Lake District species is undoubtedly C. abyssorum, though the form 
of the receptaculum differs to some extent from Prof. Sars' description and 
agrees more closely with that of G. lacustris. 
Those who {e.g. Graeter, 1903) accept the species C. strenuus in its wider 
sense lay great stress on its variability, and it might be supposed, if their 
view is correct, that great differences would be found between individuals 
from different lakes. This is far from being the case. In general form of 
body — particularly in the expansion of the last thoracic segment — there is, 
so far as I can find, no appreciable variation. In size, in the length of the 
furca and the relative length of the furcal setye there are differences, but 
they are not great. In Table 8 I have given measurements of individuals 
from seven of the lakes. These are, in the case of the first four, averages 
from ten specimens, but in the remainder of from two to six. 
It will be seen that the smallest specimens are from Wastwater and the 
largest from Windermere and Grasmere, which is hardly according to 
expectation. Those from the " primitive " lakes agree in having the longest 
setae, together with rather long furca, but the longest furca is found in 
Grasmere. The differences are, however, by no means sufficient to bridge 
the gap between C. strenuus and C. abyssorum. 
It is rather remarkable that the colour of the Lakeland individuals is 
commonly a very pronounced yellow. The species has not, in fact, at all the 
general appearance of a limnetic form, but rather of an inhabitant of ponds 
and ditches. 
Oyclops yenustus, JS'orman &; Scott. 
Syn. C. crimtus, Graeter, 1908. 
Cyclops venustus was described in 1906 * from specimens taken from 
marshy ground on Exmoor. It has since been found by Mr. D. J. Scourfield 
on Exmoor and Dartmoor, and by me in the Bog of Allen, near Newbridge 
in Ireland. It appears to be a species confined to lime-free waters, and may 
be included among what may be called the Sphagnophil Entomostraca, such 
as Acantholeberis curvirostris, Cliydorvs piger, Moraria brevipes, etc. 
* ' Crustacea of Devon and Cornwall,' p. 189 (London, 1906). 
