262 DIVISION III. ARTICULATED ANIMALS.—CLASS III. ARACHNIDA. 
most incomplete Crustaceans ; farther on it resembles the lobster, and at last 
it appears in the compact shape which constitutes the highest perfection of 
crustacean life.” 
CLASS III. OF ARTICULATA. ARACHNIDA. 
This class embraces the Spiders and Scorpions. Like the preceding 
class, it is composed of species which are, in a manner, not liable to 
change their form, not undergoing metamorphosis, but simple sheddings 
of the outer covering of the body. But they differ from these animals, 
as well as from the true insects, in many respects. As in the latter, 
the surface of their bodies exhibits orifices or transverse slits, named 
stigmata (but which it would be better to name pneumostomes, — mouth 
for the air, —or spiracles, that is, respiratory orifices), serving for the 
entry of the air, but being few in number (eight at most, generally only 
two), and situated only on the under side of the abdomen. Respiration is 
eflected either by means of aerial branchie, serving as lungs and enclosed 
in bags, to which these spiracles form the entry, or by means of radiating 
tracheew. The organs of sight consist only of minute simple ocelli, grouped 
in different positions when there is a number of them. The head, generally 
united to the thorax, merely exhibits at the place of the antennw two articu- 
lated pieces, like small didactyle or monodactyle claws, which have been 
injudiciously compared to the mandibles of insects, and so named ; but they 
move in a direction opposed to the motion of mandibles, or up and down, 
assisting, nevertheless, in eating, and replaced, in those Arachnida which 
have the mouth formed into a siphon, or sucker, by two pointed plates, used 
as lancets. A sort of lower lip (dabiéum, Fab.), or rather tongue (lan- 
guette), formed by a pectoral elongation ; two maxillw, formed of the basal 
joint of two small feet or palpi, or of an appendage or lobe of the 
same joint; a piece concealed beneath the mandibles, and called the sternal 
tongue by Savigny in Phalangium capticum, and which is composed of a 
beak-like prominence, produced by the union of a very small epistome or 
clypeus, terminated by a very small triangular upper lip, and of a Jongi- 
tudinal lower rib (caréne), generally very hairy. These, together with the 
pieces called the mandibles, generally constitute, with certain modifications, 
the mouth of the majority of the Arachnida, ; 
“The majority of the Arachnida feed upon insects, which they seize alive, 
or upon which they fix themselves, and from which they suck their juices. 
Others live as parasites upon the bodies of vertebrated animals. There are, 
howeyer, some which are found only in flour, cheese, and upon various yege- 
