44 
POPULAR SCIENCE REVIEW. 
The freshwater Entomostraca, as we have at the commence- 
ment observed, are to be found in great numbers in our ponds 
and ditches ; and though they may be observed during most 
months, it is in summer and autumn that they are to be seen in 
greatest abundance. 
At that season of the year, then, let us seek some quiet spot, 
a little way from town, and turn to “ Where the pool stands 
mantled o’er with green,” and see if we can discover any of our 
little friends lurking there, or playing “amid the floating verdure” 
which covers the surface. A small hand-net cautiously intro- 
duced, and, when removed, washed out into a small basin of clear 
water, will furnish us with hundreds of the objects we are in 
search of. First and foremost we see a creature of somewhat 
tolerable dimensions and oval shape, transparent almost as glass, 
except a rather broad dark streak running down through the 
centre of its body* and a large spherical black spot placed right on 
its forehead. It ; is furnished with a pair of powerful-looking 
branched organs projecting from its head, which may be seen 
waving to and fro in almost constant motion, so that the animal 
is seldom at rest, but is perpetually moving by short sudden 
bounds through the water. This is the common water-flea with 
branched horns, the Daphnia pulex * (figs. 5, 6). 
This water-flea is really a beautiful animal as seen through 
the microscope, and its history will well repay our attention for 
a short time. 
valves, joined together on the hack ; by having fewer pairs of feet, chiefly 
branchiform, and adapted for respiration and not locomotion ; and by having 
two pairs of feelers or antennae, the inferior of which are large, branched, 
and perform the functions of swimming organs. 
This order contains the various kinds of branched-horned water-fleas, 
the Daphnice and Lyncei. 
The second legion, the Lophyropods, are likewise divided into two 
orders : — 
1. OsrRAC0DA,t Ostracods ; which are characterised by the animals having 
the body enclosed entirely in a covering of two valves, resembling a bivalve 
shell $ by the gills or branchiae being attached to the hinder jaws j and by 
having only two or three pairs of feet, chiefly adapted for progressive motion. 
This order contains the little creatures known as the Cypriotes, &c. 
2. Copepoda,! Copepods; which are characterised by their having the 
body more distinctly annulose than those of the other orders, and covered 
by a buckler which encloses head and thorax ; and by having five pairs of 
feet adapted for swimming. 
This order contains the shell-insects known as the Cyclops, or four-horned 
water-fleas, and allied genera. 
* Legion, Branchiopoda ; order, Cladocera ; family, Daphnia dee. 
t Ostrakon (G.), a shell, 
f Kope (G.), an oar ; pous (G.), a foot. 
