History of British Entomostraca. 311 
tached notices such as I have mentioned above, one species only of this 
genus seems to have been noticed by authors, which, like all the other 
Entomostraca then known, was arranged, and described under the 
general name Monoculus. He wasthe first todividethe different ani- 
mals which figured under this name into distinct genera ; and having 
discovered in the marshes, and on the shores of Denmark and Norway, 
a variety of species all agreeing in generic characters with each other, 
he formed them into one distinct genus, and gave the name of Cyclops 
to it. He has given a great many interesting particulars of many of 
these little creatures, but has fallen into two or three mistakes con- 
cerning them, which will be pointed out hereafter. Sometime after 
Muller, Ramdohr, in 1805, published in his work on the Monoculi* 
a very correct account of the anatomy, &c. of three of the species of 
this genus found in fresh water, accompanied]with plates, which pos- 
sess very considerable accuracy ; and traces their whole transforma- 
tion from the egg to the perfect insect. Louis Jurine (pere)t is 
the last author whom we shall mention, and is the one who, of all 
that have written upon this class of insects, has given us the fullest, 
most interesting, and most accurate information upon the fresh wa- 
ter species of this genus ; and though he declines the name of Cy- 
clops, which Muller had given it, and prefers the old term Monocti- 
lus, he has cleared up the mistakes which the former has fallen into, 
and completed, by a series of wonderfully careful experiments, the 
previous discoveries ofLeeuwenhoek and De Geer. He takes no no- 
tice of the labours of Ramdohr, and seems to be ignorant of his disco- 
veries, though the work of Ramdohr preceded his by fifteen years. 
Anatomy f . In general form and appearance, the genus Cyclops 
approaches nearer to the terminating series of the Malacostraca, 
than do any other of the Entomostraca. The body of the animal, 
which is soft and gelatinous, is inclosed within a horny shell, which 
covers it like a buckler, but opens inferiorly to give issue to the an- 
tennae, organs of the mouth and feet. In general the body and tail are 
pretty easily to be distinguished from each other, and are composed 
of about ten segments, the body generally having four, and the tail 
six. In the upper or cephalo-thoracic segment of the body, which 
novos Cyclopes fluviatiles publici juris feci, nempe Monoculus quadricornis En- 
tomologis innotuit." Entomost. p. 100. 
* Beytrage zur Naturgeschichte einiger deutschen Monoculus-arten, 4to, 
Halle, 1805. 
f Histoire des Monocles qui se trouvent aux environs de Geneve.-1820. 
\ I have, in a great measure, followed Jurine in the anatomical nomenclature, 
adhering as closely as possible to the terms he uses. 
" Cancris macrouris maxime acccdunt structura corporis pcdum et antenna- 
rum, &c," Muller, p. 100. 
