THIRD GREAT DIVISION OF THE ANIMAL 



KINGDOM. 



CRUSTACEA, ARACHNIDES, AND INSECTA: 



OR ARTICULATED ANIMALS WITH ARTICULATED FEET(l). 



These last three(2) classes of the Articulata, which were 

 united by Linnaeus under the general name of Insecta^ are 

 distinguished by at least six(3) articulated feet. Each articu- 

 lation is tubular, and contains the muscles of the succeeding 

 one, which always moves by gynglymus, that is, in but one 

 direction. 



The first articulation, which attaches the foot to the body, 



(1) For the sake of brevity, I have designated them by the term Condylopes. 

 This series of articulations, of which their body is composed, has been compared 

 by some Naturalists to a skeleton, or the vertebral column. But the use of this 

 denomination is so much the more fallacious, in as much as these articulations or 

 pretended vertebrae are mere portions of thickened skin, and as this skin is continu- 

 ous, simply being thinner, and almost membranous at intervals or at the joints. A 

 general character, which serves to distinguish these animals from all other Inverte- 

 brata, consists in their exuviability, or habit of changing their skin. The situation 

 of the encephalon, pharynx, and eyes, as in the more elevated animals, establishes 

 the limits of the back and abdomen, and of their respective appendages. 



(2) Dr Leach forms a separate class of the Myriapoda. The Arachnides Tra- 

 cheariae, considered anatomically, might also constitute another, but they are so 

 closely allied to the Pulmonarije in so many other particulars, that we have not 

 thought proper to separate them- 



(3) Hexapoda. Those which have more than six, are termed by Savigny the 

 Spiriopoda. I designate them more precisely by the appellation of Hyperhexa- 

 poda, (more than six feet). 



Vol III. A 



