THIRD 

 GREAT DIVISION 



OP THK 



ANIMAL KINGDOM. 



(continued.) 



CRUSTACEA, ARACHNIDES, AND INSECTA: 



OR ARTICULATED ANIMALS WITH ARTICULATED FEET*. 



These last three f classes of the Articulata, Avhich were united by 

 Liim<eus under the general name of Insecta, are distinguished by at 

 least six I articulated feet. Each articulation is tubular, and contains 

 the muscles of the succeeding one, which always moves by gyngly- 

 mus, that is, in but one direction. \ 



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

 which is composed of two pieces §, is called the coxa, or hip ; the 

 following one, which is, usually, nearly in a horizontal position, the 



* For the sake of brevity, I have designated them by the term Condi/lopes. This 

 series of articulations, of \Yhich tlieir 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 ver- 

 tebrae are mere portions of thickened skin, and as this skin is continuous, simply 

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

 character, which serves to distinguish these animals from all other Invertebrata, 

 consists in their exuriahiUty, 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. 



t Dr. Leach forms a separate class of the Myriapoda. The Arachnides Tra- 

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

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

 thought proper to separate them. 



X Hexapoda. Those which have more than six, are termed by Savigny the 

 Spiriojjodu, I designate them more precisely by the appellation of Hyperhexapoda, 

 (more than six feet) . 



§ In many of the Crustacea the second portion of the coxa seems to form part 

 of the thighs. The tibia, as in the Arachnides, is divided into two joints. 



h 2 



