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Show 164 AU~CIINIDES. are in a manner insulated by their male organs of generation by the claw or hook of their frontal mandibles, by their pedi: culated abdomen and its spinning apparatus, and by their habits; besides this, the Scorpions appear to form a natural transition from the Arachnides Pulmonarim to the family of the Pseudo-Scorpiones, or the first of the following order. We will therefore commence, as we have said, with the Arancides or spinners. FAMILY I. ARANEIDES. This family is composed of the genus ARANEA, Lin., or the Spiders. They have pal pi resembling little feet, without a forceps at the end, terminated at most in the females by a lit. tle hook, and the first joint of which, in the males, gives ori· gin to various and more or less complicated sexual appen· dages(l ). Their frontal chelicerre (the mandibles of authors) are terminated by a movable hook, flexed inferiorly, underneath which, and near its extremity, which is always pointed, is a little opening, that allows a passage to a venomous fluid contained in a gland of the preceding joint. There are never more than two jaws. The ligula consists of a single piece, is always external and situated between the jaws, and either more or less square, triangular or semicircular. The thorax(2) usually marked with a depression in the form of a V, indicating the space occupied by the head, consists of a single segment, (1) From all the observations that have been made on the mode of copulation of the Araneides, I am still inclined to believe that these appendages arc the genital organs. I have vainly sought for particular organs on the base ~f the abdomen of a large male Mygale preserved in spirits. We are not always to judge from analogy; for the sexual org:u1s in the female Glomeris, Julus, and other Chilognatha, are situated near the mouth, a fact of which no second exam· pie is to be found. (2) The term cepltalo-tlurrax, wou hl be more strict and proper; not being in use, however, I have thought it best to n\loid it; neither will I employ that of rorsekt, although generally admitted, because, with respect to the Coleoptera, Orthoptera, &c. it only ;tpplics to the prothorax ot· first thoracic segment. PUL~IONARllE. ' 165 osteriorly to which, by means of a short pedicle, is suspended ~ movable and usually soft abdomen ; it is always furnished, under the anus, with from four to six closely approximated cylindrical or conical, articulated ~ammillm with fleshy e:tremities, which are perforated With numberless small onftces( l) for the passage of silky filaments of extreme tenuity proceeding from intern~l reservoirs. The legs, iden~i~al as to form, but of different s1zcs, are composed of seven JOints, of whioh the two first form the hip, the third the thigh, the fourth(2) and fifth the tibia, and the two others the tarsus: the last is terminated by two hooks usually pectinated, and in sever. al by one more, which is smaller and not dentated. The intestinal canal is straight, consisting of a first stomach composed of several sacs, and then of a second stomach or dilatation surrounded with silk. According to the observations of M. Leon Dufour-Ann. des Sc. Phys. VI-it occupies the greater part of the abdominal cavity, and is immediately enveloped by the skin. It iR of a pulpy consistence, and is formed of granules(3), whose individual excretory ducts unite in several hepatic canals, which pour the secreted matter into the alimentary tube. In the middle of its superior surface is a depressed line, where the heart is lodged, and which divides that organ into two equal lobes. Its form, like that of the abdomen, varies according to the species; thus in the Epeira sericea its contour is festooned. In this subgenus, as in the Lycosa tarentula, its surface is covered with a whitish coat split into areolre, which, in several species, arc easily perceived through the glabrous skin; they may be seen obeying the impulse communicated to them by the systole and (1) These holes are pierced in the last segment, which is fl·equently retracted. If it be st~:ongly compressed, very small mammilla:, (at least in some species,) perforated nt the extremity, are protl'tlded-they are the tme fusi or spinning apparatus. Some naturalists think that the two smaller mammilla:, situt\ted in the middle of the four exterior ones, furnish no silk. (2)' This joint or the first of the tibia i:~ a kind of patella. (:l) The live1· of the Scorpions is composed of pyrami(lal :tnd fasciculated lobules, a cit·cum~:~tance which scemi to announce a. mot·e advanced degree of organization. |