ARTICULATED ANIMALS, 



PROVIDED WITH ARTICULATED FEET; 



CRUSTACEA, ARACHNIDA, AND INSECTS. 



These three last classes of articulated animals, which Lin- 

 naeus united under the name of Insects, are distinguished by 

 articulated feet, at the least six in number. Each articula- 

 tion is tubular, and contains in its interior the muscles of the 

 following articulation, which always moves by ginglymus, 

 that is to say, in one direction only. 



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

 and which is most frequently composed of two pieces, is 

 named the haunch ; the following, which is usually in a situ- 

 ation nearly horizontal, is the tliigh ; the third, most usually 

 vertical, is named the leg ; finally, there remains a series of 

 little ones, which rest upon the ground, and properly form 

 the iarsus. 



The hardness of the calcareous, or corneous envelope of 

 the greater number of these animals, is referrible to that of the 

 excretion which interposes between the dermis and the epi- 

 dermis, which in man is termed the rete mucosum. It is 

 also in this excretion that the colours, frequently so brilliant 

 and so various which adorn them, are deposited. 



These animals always have eyes, which may be of two 



K 2 



