fangs, which communicate with a poison vesicle, the spider despatches the insects struggling in his toils, which otherwise he could not so easily master, and having sucked out their juices casts away the carcass. The fang, by folding upon the apex of the busal joint of the organ we are considering, which is toothed on each side, and has a channel to receive it when unemployed, can be formed into a forceps, resembling that which arms the anterior thoracic leg of the shrimp, or that of the mantis, and which is probably, in some circumstances, used for prehension. The subject of poison-fangs affords a striking example of the adaptation and modification of different parts and organs to the discharge of the same or similar functions, according to the circumstances in which an animal is placed; the viper, the centipede, and the spider have their sting in their mouth, or in its vicinity; the scorpion and the bee and wasp have it at the other extremity of the body; while the male of the Ornithorhynchus, or Duck-bill, and Echidna, or New Holland Porcupine, have it in their hind legs. Considering the evident affinity between these last animals and the birds, their poison-spur seems evidently analogous to the spur that distinguishes the males of many gallinaceous birds; and, reasoning from analogy, we may conclude that this organ is given to the males of the Monotremes as a weapon to be used in their mutual combats. Whoever examines the underside of a spider will find the feelers and the eight legs arranged nearly in a circle, with their first hip-joints parallel; with some this joint in the feelers is dilated, but in others it is of the same shape with the analogous joint of the legs, only a little longer. It forms the maxilla or under-jaw, and between the first pair is the under-lip. The function of the maxilla is to assist the, so called, mandibles, in pressing out the juices of the flies and other insects submitted to their action, and the analogous and parallel joints in the eight legs add some momentum to it. The Palpi, or feelers-which in some cases emerge from the side of the maxilla, and appear a distinct organ, and in others are merely a continuation of it-in one sex undergo a singular conversion, and discharge a function connected with reproduction; and in the other, the female, are said sometimes to assist in supporting the egg pouch, which many of these creatures carry about with them, and guard with maternal solicitude. It has been made a question by physiologists what the mandibles, and maxilla with their palpi, of the Arachnidans really represent; whether they are the analogues of organs bearing the same name in Hexapod Condylopes, or of others to be found in the Crustaceans or Myriapods. Latreille, in his latest work, regards the pieces immediately following the upper lip as analogues of the same parts in the Crustaceans, namely, a pair of palpigerous mandibles, two pairs of pediform maxillæ, and two pairs also of maxillary feet, analogous to the four anterior feet of insects. Of the above organs, the mandibles and two pairs of maxillæ may be regarded as having their prototype in the Hexapods; for the second pair of maxillæ of the Crustaceans, in the Chilognathans, is the piece that represents the labium, or under-lip, of the first named animals. Savigny, however, is of opinion that the auxiliary maxilla, or, according to Latreille, maxillary feet, of the crab, except the first pair, become the mandibles and maxilla of the spider; and that the thoracic legs of the same animal, with the same exception, become also its ambulatory legs: thus accounting for the reduction of the number of the latter from ten to eight, perhaps he was induced to adopt this opinion, with respect to the oral organs, by considering the mandibles of the spider as analogous to the poison-fang which arms the second pair of auxiliary feet of the Scolopendra. I feel, however, rather inclined to adopt the opinion of the former learned entomologist, from the consideration of an Arachnidan, which seems evidently to lead towards the Hexapods. The animal I allude to is one of ancient fame, of which, once for all, I shall here give the history. Elian relates that a certain district of Ethiopia was deserted by its inhabitants in consequence of the appearance of incredible numbers of scorpions, and of those Phalangians which are denominated Tetragnatha, or having four jaws. An event mentioned also by Diodorus Siculus and Strabo.3 Pliny likewise alludes to this event, but calls the last animal Solpuga, a name which, in another place," he says was used by Cicero to designate a venomous kind of ant. The epithet Tetragnatha, applied by Ælian, &c. to the animal which, in conjunction with the scorpion, expelled the Ethiopians, as just stated, from the district they inhabited, seems clearly to point to the Solpuga of Fabricius, for any per 4 Hist. Nat. 1. viii. c. 29. This name seems derived from the Greek. Heliocentris. 5 L. xxix. c. 4. son, not skilled in natural science, would, when he saw the expanded forceps of their mandible, pronounce that they had four jaws; and the animals of this genus, in their general form and aspect, exhibit no small resemblance to an ant, so that it is not wonderful that Pliny should regard them as a kind of venomous ant. It seems, therefore, almost certain that the ancient and modern Solpuga are synonymous. Pliny, indeed, mentions a certain kind of spider-one of which he describes as weaving very ample webs-under the name Tetragnathii; but these appear to have no connection with the Phalangia tetrag natha of Ælian, &c. Olivier was the first modern naturalist who described the animals now before us, to which he gave the generic appellation of Galeodes; but if, as the above circumstances render very probable, they are really synonymous with the ancient Solpuga, that name, revived by Fabricius, should be retained. Whether these animals are really as venomous and maleficent as they were said to be of old, and as their terrific aspect may be thought to announce, seems very doubtful. We learn from Olivier that the Arabs still regard their bite as mortal, and that the same opinion obtains in Persia and Egypt; and Pallas relates several facts, which, he says, he witnessed himself, which appear to prove that, unless timely remedies are applied, they instil a deadly venom into those they bite. Oil is stated to be the best application. On the other hand, Olivier, who found these Arachnidans common in Persia, Mesopotamia, and Arabia, affirms that every night they ran over him, when in bed, with great velocity, without ever stopping to annoy him; no one was bitten by them, nor could he collect a single wellattested fact to prove that their bite was so dangerous: to judge by the strong pincers with which the mouth is armed, he thought it might be painful, but he doubts whether it is accompanied by any infusion of venom. The mandibles have clearly no fang with a poison pore, like those of the spiders.* To return from this digression. I principally mentioned this tribe of animals, because, as was long ago observed by Walckenaer, and the observation was repeated by L. Dufour, the head, in them, is distinct from the trunk; and, as well as Phrynus and Thelyphonus, it has only six thoracic legs: so that, as the latter writer remarks, though its physiognomy and manners arrange it naturally with the Arachnidans, these characters exclude it from them. Latreille, indeed, seems to regard 1 2 L. Dufour. Annal. Gener, des Sc. Nat. iv. t. lxiv. f. 7. a. 4 Ibid. 20. the head and trunk of this animal as not distinct, but as forming together what he names a cephalothorax, or headthorax; yet he admits that the three last pairs of legs are attached to as many segments of the trunk, which certainly infers the separation above alluded to. 1 Savigny says, with respect to the feelers of Solpuga, that they, and the two anterior legs, so closely resemble each other, that they may either be called feelers or legs; but in the species described by L. Dufour, and another in my cabinet, this is not altogether the case, for the feelers, though pediform, are not terminated by a claw, but by a membranous vesicle, from which issues, when the animal is irritated, an apparatus probably used as a sucker, and which gives them a prehensory function; while the organs that represent the anterior pair of legs of the other Arachnidans, at the base of their maxillary or sciatic joint, are soldered, as it were, to the corresponding joint of the feelers, with which they agree in the number and kind of their articulations, except that they do not protrude a sucker; neither are they armed with a claw like the other legs, but are probably simply tentacular, or exploratory. There seems no slight analogy between these united maxillæ and what Savigny denominates the first and second pair of maxillæ of the millepedes, also united, which appear to me to represent the lowerlip and maxillæ of the hexapods, and in this case the two pair of feelers that issue from the coxo-maxillæ, as they are sometimes called, or sciatic joints in the Solpuga, may be regarded as representing the labial and maxillary feelers of the hexapods; the second pair are also analogous, both in their place and their function, to the first pair, or tentacular legs of Thelyphonus and Phrynus. In the Solpuga, the labium, or under-lip of the spiders, is represented by a bilobed organ, which Savigny calls a sternal tongue. From the consideration of this animal we seem to have obtained the elements, or type, in reference to which the oral, prehensory, and locomotive organs of the Arachnidans were formed; that their mandibles, maxillæ, and feelers; their second maxillæ, and the, so called, anterior legs emerging from them, are analogous to the mandibles, labium and labial feelers, and maxillæ and maxillary feelers of the hexapods; and the remaining three pairs of legs, of their six legs; the sternal tongue, so called by Savigny because it is a process of the sternum, will thus be an organ sui generis, unless it may be regarded as, in 1 Cours D'Entomolog. 548. 3 Solpuga fatalis. 2 Galeodes intrepidus. some sort, the analogue of the prosternum of insects. If this view is correct, we have here various conversions as of maxillæ and palpi into legs; a labium into maxilla; and a prosternum into a labium. In the Pedipalps-with the exception of the scorpions,―e. g. in Thelyphonus and Phrynus, especially the latter, the first pair of legs of Octopods seem to wear the form, and in some measure to discharge the functions of antennæ. In the shepherd-spiders' all the legs in some degree, imitate antenna, especially in their tarsi, which sometimes consist of more than fifty joints, rendering them very flexible, so as to assume any curve, and fits them, as their long legs do the crane-fly, to course rapidly over and among the herbage and the leaves of shrubs, &c. When reposing upon a wall, or the trunk of a tree, this animal arranges its legs so as to form a circle as it were of rays around the body, the thigh forming a very obtuse angle with the rest of the leg, and so, though the body is so small, they occupy a considerable space; but, if a finger, or any insect, &c. touches them, it elevates these angles into very acute ones, so as to form a circle of arcades round the central nucleus or body, under which any small creature can pass, but if this does not succeed, it makes its escape with a velocity wonderful for an animal furnished with legs more than ten times the length of its body. In the scorpion and the book-crab, as well as the shepherdspider, the mandibles, which are short, have a movable joint, and are converted into forceps, like the anterior legs of the crab or the lobster; their feelers also, which are very long, terminate in the same way, and form an organ by which they can catch their prey; the former being armed besides with a long jointed tail, furnished at the end with a sting, which they can turn over their back, and thus, either annoy their assailants, or despatch any captive whose resistance they cannot otherwise easily overcome. To what a variety of uses are analogous organs applied in the diversified instances here adduced; and in all these variations from a common type, how apparent are the footsteps of an intelligent First Cause, taking into consideration the intended station and functions of every animal, and how the structure may be best adapted to them, not only in general, but in every particular organ. As far as we can lift up the mystic veil that covers the face of nature, by means of observation and experiment, we find 1 Phalangium. 2 Tipula 3 Chelifer, Obisium, &c. |