THE SECOND CLASS OF ARTICULATED ANI- 

 MALS, AND PROVIDED WFTH ARTICULATED 

 FEET. 



THE ARACHNIDES 



Are, like the Crustacea, deprived of wings, and likewise not 

 subject to change form or undergo metamorphoses, but merely 

 moult or change skin. They have also the sexual oi-gans 

 remote from the posterior extremity of the body, and situated, 

 with the exception of those of several males, at the basis of 

 the belly. But they differ from these animals as well as from 

 insects in many points. In the same manner, as in the latter, 

 their body exhibits at its surface some apertures, or transverse 

 clefts, named stigmata, destined for the entrance of air, but 

 few in number (eight at most, more commonly two), and in- 

 variably situated at the lower part of the abdomen. Respira- 

 tion otherwise is performed, either by means of air-gills per- 

 forming the office of lungs, enclosed in pouches, of which 

 these apertures form the entrance, or by means of radiated 

 tracheae. The organs of vision consist in small simple eyes 

 grouped in various ways, when they are numerous. The 

 head, usually confounded with the thorax, presents, in place 

 of antennae, only two articulated pieces, in the form of small 

 didactylous or monodactylous claws or forceps, which have 

 been erroneously compared to the mandibles of insects, and 

 similarly designated. They move in a diiferent direction, or 



