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 cEsophagus, is denominated the brain. Of the senses, properly so 

 called, 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 little 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 Molluscous Animals, 

 (Animalia MoUusca.) 



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 oesopliagiis, 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 Articu- 

 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 tracheae, 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 Zoophytes. 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 bodies. The intestines of the greater number consist merely in a 



IT'. 



