384 
CLASS ARACHNIDA. 
from above downwards, assisting, nevertheless, in manduca- 
tion, and replaced in the Arachnides, whose mouth is in the 
form of a siphon or sucker, by two pointed laminae, which 
serve as lancets. A sort of labium, or rather tongue, produced 
by a pectoral elongation ; two jaws formed by the radical 
articulation of the first articulation of two small feet or palpi, 
or by an appendage or lobe of this same articulation ; a piece 
concealed under the mandibles, called sternal tongue , by 
M. Savigny (Description and figure of the phalangium 
copticum ) , and which is composed of a projection in the form 
of a bill, produced from the union of a very small epistoma, or 
hood, terminated by a very small triangular labrum, with a 
lower longitudinal keel, usually very well furnished with hair; 
all these, with the pieces called mandibles, constitute generally, 
with some trifling modifications, the mouth of the arachnides. 
The pharynx is placed in front of $ sternal projection, winch 
has been considered as a labrum, but which, from its imme- 
diate situation behind the pharynx, and the absence of palpi, 
is rather a tongue. The feet like those of insects, are com- 
monly terminated by two hooks, and sometimes by one more, 
and all annexed to the thorax (or rather cephalothorax), 
which, a small number excepted, is formed but of a single 
articulation, and very often closely united to the abdomen. 
This last part of the body is soft or but ill defended in the 
majority. 
Considered in the relation of the nervous system, the 
arachnides are strikingly remote from the Crustacea and in- 
sects. For if we except the scorpions, which, in consequence 
of the knots or articulations forming their tails, have some 
additional ganglia, the number of these swellings of the two 
nervous cords, is three at most, and even in these last 
animals, taken altogether, it is no more than seven. 
Most of the arachnides live on insects, which they seize 
living, or on which they fasten and suck the juices. Others 
