OUR FRESHWATER ENTOMOSTRACA. 
51 
for the rarer kinds of Entomostraca, which are well worthy of 
a visit. On the banks of the Thames, nearly opposite the vil- 
lage of Isleworth, not far from Richmond, there is a famous ditch 
which produces an immense number of both plants and animals. 
In one spot of no great extent, a successful haul of the net 
will bring to our view a multitude of Entomostraca. Amongst 
these we will find a very delicate transparent creature, which 
has been well described as 66 having a head all eye.” This has 
been named by Muller the Polyphemus * oculus (fig. 16). 
Constructed somewhat like a daphnia, this animal appears 
formed of a large black head, and still larger transparent body. 
The feet are four pairs in number, but do not appear to be 
contained within the shell, projecting, as it were, outside of it. 
The branched horns or feelers, like those of the daphnise, are 
large, and serve the animal as organs of progressive motion. 
The head is prominent, and appears to consist chiefly of a large 
black mass placed prominently on its forehead. This is its 
eye, is very large, is provided with a set of muscles which give 
it a semi-rotary motion, and is beset all round the upper and 
outer edges, with about twenty lucid crystalline lenses. The 
large lower portion of the shell serves as a matrix, or receptacle 
for containing the eggs. These are few, generally only about 
six in number. This little polyphemus appears to be a very 
delicate creature, and is very difficult to be kept long alive in 
captivity. 
In this same ditch, we find, along with the polyphemus, 
numbers of little Entomostraca, belonging to the same large 
group as it and the dpcphnise. These animals (the Lynceidce) 
are contained within a fine transparent shell, have much smaller 
horns or antennae than the daphniae, have the stomach, which 
runs through the whole length of the animal, convoluted, that 
is, forming one and a half complete twist or turn round itself, 
and in addition to the eye, which is so prominent a figure in 
this group, they have a small black spot at a little distance 
in front of it. The species we have selected for representation 
is the Harp-shaped Lynceus, the Acroperus harpce] (fig. 17), 
a remarkably pretty creature and full of energy. Owing to the 
comparative smallness of the branched horns or feelers, the 
lyncei, instead of swimming by irregular bounds, like the 
daphnise, direct themselves by rapid motions of these organs 
straight towards the point to which they wish to go. Their 
habits and economy are very much the same as those of the 
* Polyphemus, the giant celebrated in the TEneid of Virgil, as having only 
one eye in the centre of his forehead. Legion, Branchiopoda ; order, Clado- 
cera. 
f Legion, Branchiopoda ; order, Cladocera ; family, Lynceidce . 
VOL. VI. — NO. XXII. F 
