PULMONARI^. 
278 
never exceeds four, and is most generally but two ; sometimes they 
are hardly perceptible, or even annihilated. The organ of respiration 
is formed of little laminae. The heart is a large vessel which extends 
along the back, and gives off branches on each side and anteriorly*. 
There are always eight legs. The head is always confounded with 
the thorax, and presents at its anterior superior extremity two man- 
dibles — so called by authors, the chelicerce or antenne-pinces ^ Latr. 
—terminated by two fingers, one of which is moveable, or by a single 
one resembling a hook or claw that is always moveablef. The mouth 
is composed of a labrumj, of two palpi, sometimes resembling arms 
or claws, of the two or four jaws, formed, when there are but two, by 
the radical joint of these palpi, and moreover, when there are four, by 
the same joint of the first pair of feet, and of a ligula consisting of 
one or two pieces §. If we base our arrangement on the progressive 
decrease of the number of pulmonary sacs and stigmata, the Scorpions 
where it is eight, while in the other Arachnides it amounts to but 
four or two, should form the first genus of this class, and consequently 
our family of the Pedipalpi should precede that of the Araneidesl[. 
But the latter Arachnides are in a manner insulated by their male 
organs of generation, by the claw or hook of their frontal mandibles, 
by their pediculated abdomen and its spinning apparatus, and by their 
habits ; besides this, the scorpions appear to form a natural transition 
from the Arachnides Pulmonariae to the family of the Pseudo-Scor- 
piones, or the first of the following order. We will therefore com- 
mence, as we have said, with the Araneides or spinners. 
* According to Marsel de Serves, M^moire sur le Vaisseau Dorsale des Insectes, 
the blood, in the Aranfeides and Scorpions, is first directed to the organs of respiration, 
and thence proceeds to various parts of the body through particular vessels. Judg- 
ing, however, from the affinity of these animals to the Crustacea, the circulation 
would seem to be effected in the contrary direction. See the Memoir of Treviranus 
on the Anatomy of Spiders and Scorpions. 
f These parts are formed of a first very large and ventricose joint, one of whose 
superior angles, when the chelae are didactyle, forms the fixed finger, and of a second 
joint, that which forms the opposite and moveable finger or the hook, when there is 
but one finger. In the latter case, as with several of the Crustacea, I will employ 
the term claw. 
X See our general observations on the class. 
§. That of the Scorpions appears to be composed of four pieces, forming an elon- 
gated and pointed triangle, directed forwards ; the two lateral ones however are 
evidently formed by the first joint of the two anterior feet, and may be considered 
as two jaw’s analogous to the first. We see by Mygale, Scorpio, &c., that the palpi 
are divided into six joints, of which, in the other Araneides, the first or radical one, 
is anteriorly and internally dilated to form the maxilliform lobe. Even this lobe, in 
some species, is articulated at base, and thus becomes a maxillary appendage of this 
same joint. Exclusive of this joint, the pulpus consists of but five, and such is the 
most usual mode of supputation. In the Scorpions the moveable finger of the for- 
ceps, as in that of the Crustacea, forms the sixth joint. 
11 In my Fam. Nat. du R^gne Animal, I begin with the Pedipalpi. M. Leon 
Dufour also thinks that the Scorpions should come first. 
