24 THE ANIMAL KINGDOM. 
remote from each other; and the gradation of the same general plan is to 
be traced from Man down to the lowest of the fishes. 
In the second conformation, peculiar to animals, there is no internal frame- 
work, or skeleton. The muscles are simply attached to the skin, which forms 
a soft and contractile covering, from which proceed, in many species, stony 
plates or envelopes, denominated shells, of which the position and produc- 
tion are analogous to that of the mucous body. The nervous system is, 
with the viscera, included in this general covering, and is composed of many 
scattered masses, united by nervous threads. The principal of these, placed 
upon the wsophagus, is denominated the brain. Of the senses, properly so 
salled, the organs of taste and sight are alone to be distinguished, and even 
these are sometimes wanting. One family alone exhibits the organs of 
hearing. This division, however, is always characterized by a complete 
circulating system, and particular organs for respiration; and the organs 
of digestion and secretion are litile less complicated than those of the verte- 
brated animals. Though the general plan of their organization be not so 
uniform in regard to external configuration, as the preceding division, yet 
even between these parts, there is always an analogous resemblance in 
structure and functions. This division is termed Moriuscovs AnNIMALs, 
(Animalia Mollusca.) 
The third general form is that which is observed in insects, worms, &c. 
Their nervous system consists of two long cords, extending along the belly, 
swelled out at intervals, and uniting into knots, or ganglia. The first of 
these, placed upon the esophagus, though held analogous to the brain, is but 
little larger than the others. The covering of the body is divided by trans- 
verse folds, into a certain number of rings, of which the teguments are in 
some hard, in others soft, but to the interior of which the muscles are always 
attached. Articulated limbs are often attached to the sides of the annulated 
portions of the trunk, but it is also frequently destitute of those organs 
of movements. To these animals, Cuvier has given the name of Arricu- 
LATED ANIMALS, (Animalia Articulata.) 
In this division is observed the transition from the circulating system in 
closed vessels, to a nutritive process, by simple imbibition; and also a cor- 
responding transition from respiration, by circumscribed organs, to respira- 
tion performed through the medium of trachee, or air-vessels, dispersed 
through the body. The organs of taste and sight, are very evident in the 
animals of this division. Their jaws, when they have any, are invariably 
lateral. One family alone possesses the organ of hearing. 
The animals comprehended under the fourth general form, are usually 
known by the name of Zoopuyres. They approach, in structure, to the 
homogeneous character of plants. Neither a distinct nervous system, nor 
particular organs of sense, are perceptible, and but obscure vestiges of cir- 
culation. Their respiratory organs are almost always on the surface of 
their bolies The intestines of the greater number consist merely in a 
Dsl 
