310 History of British Entomostraca. 
is very brief, and the figure which he gives is very bad ; being bare- 
ly sufficient to enable us to make out that it is the Cyclops quadri- 
cornis that it is meant to represent. Leeuwenhoek appears to have 
been the first to have taken any lengthened or particular notice of 
the genus. In his " Epistolaead Societatem Regiam Anglicam," &c. 
(Epistola 121, written in 1699,) he gives a good many details of an 
insect which he found in fresh water, and whose habits he seems to 
have studied with considerable attention. He gives a figure of it 
also, which, though far from being correct, suffices to shew us that 
his insect is also the C. quadricornis. His observations upon it are 
very interesting, and he discovered amongst other things worthy of 
note, the great difference there is between the young and old in- 
sects, though he did not carry his observations so far as to trace the 
transformations which take place. In " No. 283 of the Philosophi- 
cal Transactions, for January and February 1703," the same au- 
thor gives a description of a polype (the Hydra viridis of Muller) 
growing upon the Lemna or duck-weed, which calls forth another 
paper from an anonymous correspondent in " No. 288 for November 
and December 1703," in which the writer mentions his having fre- 
quently observed the same polype growing upon insects, especially 
upon " two sorts of the crustaceous kind." These two species of in- 
sects, which he states are monoculous, he -gives figures of, sufficient- 
ly correct to shew them to be the C. quadricornis and Castor, the 
first being a tolerable figure, though they second is very indifferent. 
The same writer also takes notice of a third insect of the same ge- 
nus, which is much smaller and like a shrimp, but which he could 
never figure, evidently the C. minutus. Baker in his " Microscope, 
made easy, 1743," makes a few remarks upon these same insects, and 
copies the figures from the Philosophical Transactions, and in his 
" Employment for the Microscope, 1764," he publishes a letter from a 
correspondent, who gives a variety of details with regard to the insect 
which Leeuwenhoek describes, finds great fault with his figure, but 
gives a much worse one himself ! De Geer in his " Memoires pour 
servir al'histoire deslnsectes," Vol. vii. published in 177&, is the next 
author, I believe, who has entered into any details with regard to any 
of the insects of this genus. He describes at considerable length, and 
figures with tolerable accuracy, the C. quadricornis, and confirms 
many of Leeuwenhoek's statements with regard to it, particularly 
the great difference between the old and the young insect. Otho Fri- 
dericus Muller,* is the next succeeding author who has particularly 
noticed this genus. Previous to his time,t with the exception of de- 
* Entomostraca, seu Insecta testacea, &c. 1785. 
f " Unicum quidem ante annum 1769, quo in Synopsi Monocular urn rjuatuor 
