688 
M O N O 
are without any; it has one or two eyes, notwithstanding 
its name pionocnfus; when there are two eyes, they ap¬ 
proximate, and are fixed in the fhell; there are four feel¬ 
ers, in continual motion when fwimming; the hind ones 
are very fmall, and hook-fhaped. There are more than 
feventy fpecies, feparated into eight divifions. They are 
found chiefly in Europe, a few in India, commonly in 
muddy ditches, frequently in fea-waters, often paraiitic 
on fuci, confervas, ulvse, and other aquatic plants. Many 
inhabit our own ditches or fea-coafts. By far the greater 
part are very fmall water-infe&s, requiring the afliftance 
of the microfcope for the inveftigation of their particular 
organs; fome, however, as we fhall fee, are fo large as to 
require no very minute infpedtion; and o,ne fpecies is of 
a lize fo gigantic that it is generally confidered as the 
largeft of the whole cruftaceous tribe. This is the poly- 
phemus, and will be found in the feventh divifion. 
I. Cyclops; with a Jingle eye and cruftaceous body. 
1. Monoculus oculus, the hornlefs monoculus. In this 
fpecies there are no antennae, but two feelers, which are 
long and branched ; the tail is infiedted. The infedts of 
this fpecies are,found in the pools and ftagnant waters in 
many parts of Europe; they fwim in fvvarms, upon their 
back; each infedt has a large black eye, which appears to 
occupy the whole of the head. 
2. Monoculus quadricornis, the four-horned monocu¬ 
lus : antennae four, branched ; tail ftraight and bifld, the 
divifions branched. It is found in different parts of Eu¬ 
rope, and in the ftagnant waters of this country. It is a 
very minute infect; and is well known, being very com¬ 
mon in almoft every ftagnant water, and fometimes makes 
Its appearance in that of pumps and wells, and is accord¬ 
ingly obfervable frequently in water brought to table. 
In the annexed Plate, this infedt is fhown, greatly mag¬ 
nified, at fig. i. The body is of an afhen-grey, fometimes 
inclining to green. From the head arile four antennae; 
two forwards, a, a, and two backwards, b, b. Betwixt 
the four antennae, quite on the fore part of the head, is 
fituate a Angle eye, c. From the head to the tail the body 
goes gently decreafing in lhape; it is compQfed of feven 
or eight rings, which grow continually more ftraitened. 
The tail is long, divided in two ; each divifion being cu- 
rioufly branched, d, d. The female carries her eggs on 
the two lides of the tail, in two yellowifti oval bags, e, e, 
which, taken together, nearly equal the infedt in bignefs. 
It has eight hairy legs, J\ J\ wdiich lie moftly under the 
body; as it makes little ule of them, the antennas being 
of more fervice towards the leaping and fkipping which 
it performs in the water with great nimblenefs. This 
minute infedt is not half a line in length. A number of 
them being kept in a bottle of water, fome will be feen 
loaded with their eggs, after a while depofiting the two 
parcels, either jointly or feparately. 
3. Monoculus minutus, the fmall monoculus: antennae 
two, linear; the tail ending in two briftles. This infedt 
is found at the banks of ditches, generally among duck¬ 
weed, and at firft fight is thought to refemble the Lepifma 
laccharina. The number of legs is ten, which are long 
and hairy; the tail ends in two papillae. 
4. Monoculus caeruleus, the blue monoculus : antennae 
two, linear; body bluifh, with a ftraight two-lobed tail. 
It inhabits Germany, in muddy ditches. The head, the 
tail, and antennas, are red; the eyes black; abdomen 
green; legs eight. 
5. Monoculus rubens, the red monoculus : antennae 
two, linear; body reddilh, with a ftraight forked tail. 
Found in ditches and rivulets,- and is common through 
the whole year; it has eight legs. 
6. Monoculus lacinulatus: antennae two, linear, and 
white; tail curved, forked. It inhabits Germany, in 
ditches. 
7. Monoculus caftor. Monf. Jurine, in a memoir read 
before the Philomatic Society of Paris, in the year 1800, 
includes under this name the monoculi of which Muller 
C U L U S. 
very improperly (he fays) formed the three preceding 
fpecies. The caeruleus is nothing elfe, as he aiierts, than 
an old female of the rubens; and the charadter of the laci- 
nulatas confifts merely in foreign appendages, or a kind of 
infufion-animals which often adhere to this monocnlus. 
M. Jurine, having fucceflively reduced feveral of thele 
infedts to a ftate of afphyxy by means of a few drops of 
fpirits thrown into the water which contained them, and 
having revived them by adding new pure water, obferved, 
that it is not the heart, but the inteftinal canal, which 
retains longeft its irritability, and refumes it the fooneft. 
The female carries her eggs, not in two clufters, like the 
greater part of the other Cyclops, but in a large bag, 
which has a little refemblance to the tail of the beaver. 
It is from this circumftance that the author gives to the 
above fpecies the name of caftor. The right antenna oi : 
the male has a hinge by means of which he lays hold of 
the threads that terminate the tail of the female to force 
her to copulate. When the two fexes copulate, they are 
in an oppofite diredtion. 
8. Monoculus longicornis: antennae two, linear, and 
very long; tail bind. It inhabits the lea round Finmark. 
9. Monoculus captivus : antennae two, linear; head co¬ 
vered with a dilated ftiield; tail ftraight, cleft. This is 
found in Germany. It has fix legs 5 and the tail has fix 
joints. 
10. Monoculus minuticornis : antennae two, ftiort, and 
linear; tail cleft, and ending in two briftles. It is fome¬ 
times, though not often, found in fea-water. The feelers 
are about half as long as the antennae. 
11. Monoculus claviger: antennae two, fubclavate, ri¬ 
gid ; tail bifid. It inhabits, though very rarely, the rivers 
of Germany; and glides (lowly along, alternately on its 
back, fides, and belly, and fometimes it will raife itfelf 
upright. The body above is white, and red beneath ; the 
tail is without joints, and the legs are eight. 
12. Monoculus craflicornis: antennas two, dilated and 
fhort; tail bicufpidate. Sometimes found in marfliy places. 
The body is in five fegments 5 the antennas branched at 
the bafe. 
13. Monoculus curticornis: antennas two, which are 
minute and ftraight, with three hairs at the tip ; the body 
is inarticulate; the claws unarmed; the tail forked. 
14. Monoculus chelifer: antenna; two, (hort, and re¬ 
curved; body inarticulate; claws chelate; tail forked. 
Found in fea-water. 
15. Monoculus brevicornis : antennas two, thofe of the 
male hooked; the tail is let with very ftiort briftles. It 
inhabits fea-marlhes, and refembles the quadricornis. The 
antennas of the female are forked at the tip. 
II. Daphne; with a fugle eye and bivalve fell; antennae 
branched. 
16. Monoculus pulex, the water-flea: tail infledted ; 
(hell mucronate behind. This infedt derives its fpecific 
name from its peculiar ftarting or fpringing motion; it is 
almoft an univerfal inhabitant of ftagnant waters, appear¬ 
ing fometimes in fuch vaft fwarms as to caufe an apparent 
dilcolouration of the water. It is an infedt of a highly 
Angular and elegant appearance, exhibiting, when mag¬ 
nified, a beautiful diftribution of internal organs. It is 
generally about one-tenth of an inch in length, but fome¬ 
times conliderably larger. It is of an oval fliape, trun¬ 
cated in front, and fliarply pointed behind; the body is 
inclofed in a bivalve tranfparent (hell, which, when exa¬ 
mined by the microfcope, appears finely reticulated. The 
eyes of thefe animals are of a lingular conllrudtion, they 
are large in proportion to the infedt, and placed very near 
each other, and appear to confift of many leparate globules 
of a black colour, united under a common Ikin. In the 
female infedt the ovarium is generally very confpicuous, 
filling the greater part of the fpace between the (hells; 
the ova are very large in proportion to the fize of the 
animal, and the young are hatched before their exclufion 
from the parent. This animal is laid to poflefs, in an 
inferior 
