ARACHNIDES. 
276 
ment of two small legs or palpi*, or by an appendage or lobe of 
that same joint ; a part concealed under the mandibles, called langue 
sternale by Savigny — description and figure of the P halangium cop- 
ticum — and composed of a projection in the form of a rostrum, 
produced by the union of a very small clypeus, terminated by an 
extremely small triangular labrum, and of an inferior longitudinal 
Carina, usually very hairy, are the parts, which, with the pieces termed 
mandibles, constitute with some modifications the mouth of most of 
the Arachnides. The pharynxf is placed before a sternal projection 
which has been considered as a lip, but which, from being placed 
directly behind the pharynx, and having no palpi, is rather a ligula. 
The legs, like those of Insects, are commonly terminated by two 
hooks, and even sometimes by one more, and are all annexed to the 
thorax, or ratlier cephalo-thorax, which except in a small number, is 
only formed of a single segment, and is frequently intimately united 
to the abdomen. This latter part of the body is soft, or but slightly 
defended, in most of them. 
AVith respect to their nervous system, the Arachnides are greatly 
removed from the Crustacea and Insects ; for if we except the Scor- 
pions, wliich from the knots or joints forming their tail have some 
additional ganglions, the number of these enlargements of the two 
nervous coi'ds is never more than three, and even in the latter, all 
counted, it never extends beyond seven. 
Most of the Arachnides feed on Insects, which they either seize 
alive, or to which tliey adhere, abstracting their fluids by suction. 
Others are parasitical, and live on vertebrated animals. Some of 
them, however, are only found in flour, on cheese, and even on 
various vegetables.. Those which live on other animals frequently 
* They only differ from legs, properly so called, by their tarsi, which are composed 
of a single joint, and are usually terminated by a small hook, resembling, in a word, 
the ordinary feet of the Crustacea. See our general observations on the first order. 
These jaws and palpi appear to correspond to the palpigerous mandibles of the 
Decapoda, and to the two anterior feet of the Limuli. In Phalangium, the four 
following legs have a maxillary appendage at their origin, so that these four appen- 
dages are analogous to the four jaws of the preceding animals. I had described these 
parts, long before the publication of Savigny’s memoirs on the invertebrate animals, 
in a monograph of the species of this genus proper to France. From these and 
preceeding observations, it is evident that the composition of these animals is easily 
reduced to the same general type which characterizes all articulated animals with ar- 
ticulated feet. The Arachnides are not then a sort of acephalous Crustacea, as stated 
by this savant, usually so exact in his anatomical observations, of which, unfortu- 
nately for the sciences, he has become the victim. 
-f- Although Savigny admits of two oi-ifices, neither Straus nor myself can find 
but one ; it must have been the effect of an optical illusion arising from the fact 
of his having only perceived the lateral extremities of the fissure, its middle 
being concealed by the tongue with which its anterior face is thickened in its mediate 
portion. 
