POLYPHEMUS. 
113 
The intestine is curved, but not convoluted. 
The body of the animal is only partially inclosed 
within the shell. It is fleshy, and after descending in it 
about two thirds of its length, turns upon itself from be- 
hind forwards, and folds itself suddenly backwards, to 
form a long and slender tail, which projects from the shell, 
and protrudes externally, extending fully the length of the 
carapace. It is serrated on the outer edge, and terminates 
in two long setae. This organ differs very much from that 
of the Daphniae, and, as Jurine says, seems to serve as a 
rudder. 
The heart is situated at the same part of the body as 
in the Daphniae, near the junction of the head and body. 
The lower part of the shell seems to be the matrix or 
receptacle for containing the ova, which are generally 
about six in number. 
The legs (t. XVII, f. 1 b) are four pairs, always pro- 
jecting from the shell externally. They are four-jointed, 
and provided at the extremity of the last joint with 
several plumose setae. The fourth pair are shorter than 
the others, and want these setae. These organs resemble 
more the legs of the Cyclopidce than the other animals of 
this family, and are, in accordance with their structure, 
used by the Polyphemus for swimming. It always swims 
upon its back, and generally horizontally, with quick re- 
peated motions of the antennae and legs, which carry it 
rapidly through the water. 
Like the Daphniae, the Polyphemus has, at particular 
seasons, the ephippium, or saddle, which serves exactly 
the same purpose as in them. The number of young is 
not so great as in the Daphniae, seldom reaching, at the 
most, to the number of ten, but more frequently about six. 
It is very difficult to make accurate observations on the 
manners and habits of living and propagating their species 
in this genus, as the little animals are very difficult to be 
kept in captivity. In the young, even when in the matrix, 
it is particularly observable, that the eye very soon makes 
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