216 LIFE,' IN ITS INTERMEDIATE FORMS. 
• 
imbedded in the flesh, like the roots of a tree in the soil, 
resist all opposing influences to drag it away. This form 
is one of the most bizarre of the whole ; for, besides this 
strange rooting head which is concealed, the exposed body 
resembles a twisted sausage, without limbs, to which the 
external ovaries hang, like rolls of thread twined loosely 
together. 
Every ditch and pool is tenanted by tiny nimble crea- 
tures, which move through the water by a succession of 
little leaps, whence they are called Water-fleas. Some- 
times the ponds swarm with them to such a degree that 
the fluid contents seem not water but blood, or other 
strange liquid, according to the colour of the little animals. 
These belong to the Order Entomostraoa, and, though 
small, many of them being undistiuguishable without 
microscopic aid, they are highly curious. Many of them 
are enclosed, either wholly or in great measure, in a shell, 
which takes the form of two convex plates, either soldered 
together down the back, or united there by a hinge, leav- 
ing the opposite edge free for the protrusion of the head 
and feet. The close resemblance of the latter ( Cyprididce ) 
to the bivalve shells of Moll use a is remarkable. 
In general these little animals have but a single eye in 
the middle of the forehead, which is of largo size in pro- 
portion, round, and generally of a brilliant red hue, glis- 
tening like a ruby, so that it furnishes a beautiful study 
under the microscope. In the common Water-flea (Daph- 
niapulex), the eye is bluish black, evidently composed of 
about twenty crystalline lenses, and though quite in- 
cluded within the shell, its motions, which are quick and 
partly rotatory, can be distinctly perceived. 
