THE SECOND CLASS OF ARTICULATED ANI- 
MALS, AND PROVIDED WITH 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 organs 
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 different direction, or 
