ORDER BRANCHIOPODA. 
339 
entirely occupied by a large eye ; their feet are completely 
uncovered. 
As yet we know but a single one, the Polyphemus of the 
ponds , Monoculus pediculus, Linn. Deg. Insect. VII. xxviii. 
6 — 13 ; Polyphemus oculus , Midi., &c. 
According to J urine, the feet in no respect resemble those 
of the monoculi of this division. They are composed of a 
thigh, a leg, a tarsus with two articulations, and from the 
extremity of which come forth (that of the last pair excepted), 
some small fdaments. From the anterior extremity of the head 
some small antennae project, of a single articulation, terminated 
by two filaments. The shell is so transparent, that all the vis 
cera may be distinguished through it. The matrix, when it is 
full of eggs, occupies the major part of the interior of this shell. 
Their largest number does not exceed ten. When we trace 
the gradual development of the foetus, we are struck by the 
prompt appearance of the eye, comparatively to that of the 
other parts of the body : it is at first greenish, and passes in- 
sensibly to deep black. The abdomen, after being convoluted 
on itself, from behind forwards, folds suddenly backward to 
form a long, narrow, and pointed tail, from which come 
two long articulated filaments. The animal always swims 
upon its back, and most frequently horizontally, communi- 
cating to its arms or oars, and to its feet, lively and reiter- 
ated movements. It executes, with considerable nimbleness 
and agility, all sorts of evolutions. It is subject, in its youth, 
and after its first moul tings, to a malady called ephippiiim , 
but this epliippium or saddle has always a determinate figure, 
and never contains the two oval balls, which it presents in 
daphnia. In a state of captivity, this animal will not live 
long, and the young cannot be reared, at least Jurine could 
not preserve them after the first moultings, nor observe the 
progress of their generations. He did not recognize males in 
any of the individuals which he kept; in fact, he was able to 
