CRABS AND SHRIMPS. 
213 
CHAPTER XXIII. 
Crustacea ( Crabs and Shrimps). 
Continued. 
Perhaps the most singular of all animal existences, and 
certainly the most remarkable of the Class to which they 
belong, are those Crustaceans which constitute the Order 
Epizoa, so called from their parasitical habits. The grand 
principle of economy is so perfectly carried out in Crea- 
tion, that not only is every spot of inorganic nature turned 
to account in providing for some existences proper to it, 
but even the bodies of living animals are made to afford a 
dwelling-place and a feeding-ground for multitudes of 
other creatures. The intestines, the layors of muscle, the 
coats of the eye, the sinuses of the skull, afford, as we 
have already seen,* in different animals, a home for cer- 
tain creatures of strange conformation, which are found 
under no other conditions, and are thence called Intes- 
tinal Worms, or more correctly Entozoa, i. «•> animals 
which live within other animals. The gills of fishes, the 
breathing pouches, the interior of the mouth, and various 
parts of the surface of the body, become, on the other 
* See Chapter XIII., eapm. 
