on tip-toe, supporting itself by its tail. Its fore-legs are then applied so closely to the breast as to be invisible, whence the ancients call it Dipus, or biped;' having taken their spring they alight upon their fore-feet, and elevating themselves again, they are off so rapidly, that they seem to be always, so to speak, upon the wing. They use their long tail to support themselves when they recover from their leaps, giving it the curvature of the letter S reversed, thus, 2. When their tail has been shortened at different lengths, it has been found that their leap is diminished in the same proportion; and when it was wholly cut off they could not leap at all. 2 We see, in one Order of the Birds, the Waders, a remarkable disproportion of the legs to those of the rest of the Class; they look as if they walked upon stilts, whence the name of the Order, so disproportionally long are their legs to those of the generality of birds. I have before noticed the use of these legs to them in flying, but the principal object of this structure is to enable them to prey upon aquatic animals, fishes, worms, and the like. Whoever is in the habit of frequenting estuaries, and other waters, will generally see some of these birds, as herons. and bitterns, standing in them, where shallow, and ever and anon dipping their heads, and then emerging swallow their. capture. The design of this structure must be obvious to every eye, namely, to qualify these birds of prey to assist in keeping within due limits the population of the various waters of our globe, which other predaceous animals cannot come at. Another tribe of long legged birds, which Cuvier considers as belonging to the present Order, though their habits and habitat are altogether different, and which constitute his family of short-winged waders, is that to which the Ostrich and Emu belong, but in these the object of this structure is to fit them not for standing in the water, but for running in the sandy desert; and such is the velocity of the ostrich that it can outstrip the fleetest Arabian courser when pursued. Other birds are remarkable for the shortness and strength of their legs; of this description are the aquiline race, which are thus fitted by their Creator for seizing and holding fast any prey which their piercing sight discovers. 1 Herodot, Melpon, § 192. Ed. Reizii. 2 It is to be observed in general, with respect to the Class of Birds, that the conspicuous part of their legs is not the shank, which is chiefly covered, by muscle and feathers, but is formed of the tarsal and metatarsal bones united into one. 3 See above, p. 276. 5 Struthio Camelus. 4 Echassiers brevipennes. 6 Casuarius Emeu. There is one, and a very elegant bird, belonging to this Order, the secretary-bird,' the legs of which are so long, that many ornithologists have arranged it with the waders. It is, however, very properly placed amongst the predaceous birds. Its long legs are given it to enable it to pursue the serpents, which form its food. We see, in this instance, a departure from one of the typical characters of its own tribe, and those of another adopted in order to accommodate the animal to the circumstances in which it was the Divine will to place it, and to fit it for the function which it was there to exercise. Amongst the Reptiles there is little diversity, as to the relative proportions of the organs we are considering, and their parts; in the Batrachians, or frogs and toads, which are mostly leaping and swimming animals, the hind legs are elongated to accommodate them to those kinds of locomotion; and in some of the Saurians or lizards, which are approaching to the Ophidians or serpents, the legs are very short, and sometimes reduced to a single pair; even in some serpents rudiments of a pair of legs have been discovered, particularly in the Boa.* Some insects are remarkable for the vast length of their anterior pair of legs; what may be the object of this formation has not been discovered except that, in one instance, it is found only in one sex. The animal I allude to belongs to the tribe of Capricorn beetles, and seems not to be uncommon in Brazil. The fore-legs of the male are more than twice the length of the body, while those of the female, though longer than the others, are scarcely half so long. Many insects are formed, in some degree, after the pattern of the kanguroo and the jerboa, in order to enable them to transport themselves by leaping beyond the reach of their enemies. The thighs of their hind legs are incrassated so as to afford a box capable of containing muscles sufficiently powerful, by their action, to send them through the air to an almost incredible distance. If we examine the structure of the posterior legs of any common grasshopper, we immediately see, both from the position of the joints with respect to each other, and the shape and volume of the elongated thigh, that they are made for leaping. The shank, when the animal prepares to leap, forms an acute angle with the thigh, so that being suddently unbent, it springs forward, often to the distance of two hundred times its own length. Many carriages are set upon 1 Ophiotheres cristatus. Veill. 3 As in Bipes. 5 Acrocinus longimanus. 2 E. G. in Seps. 4 Zool. Journ. iii. 253. 6 Cerambyx. L. springs made to imitate the position of this insect preparing to leap, which are known by the name of grasshopper springs.1 Several beetles rival the grasshoppers in their leaps, and have their posterior thighs much disproportioned to the bulk of their bodies, which allow space for a sufficient muscular apparatus, to send them, like an arrow from a bow, to a great distance. If a finger be held to a leaf covered by the turnip-flea, in the twinkling of an eye, all skip off and vanish. We may hence imagine with what expedition they disappear at the approach of any insectivorous bird. Thus their Creator, who cares for the meanest of his creatures, has furnished them with meansof escape, to prevent their annihilation, and to preserve them in such force as may best answer his end in creating them. But besides partial modifications of the structure of these organs for particular uses, others are more general and affect the whole leg. Every one is aware how well adapted, by their fleetness, some of the Ruminant Mammalians are to make their escape from their ravenous pursuers, the most adroit and the most ruthless of which is the mighty hunter, man. If we look at the legs and hoofs of the deer tribe,3 the former long, slender, and elastic; and the latter calculated for sure footing; and if we consider besides the quickness of their senses of seeing and hearing, we see at once that their structure is the effect of design, and that the deepest intellect presided at its first fabrication. Though man, as well as every ferocious beast, pursues these beautiful and elastic animals, it is only, because he is Gulæ deditus, seldom with any view to seek their alliance, or to turn them to his purposes. There are some, however, as well as the rein-deer, cherished by the Laplander as his principal treasure, but pursued by the American savage only to be devoured, which probably might be employed with advantage, as well as the dog, in countries not suited to our beasts of burden; and it has been supposed that the Wapiti" might be trained and rendered useful; I am ignorant, however, whether any steps have ever been taken to ascertain this. But the legs, as well as instruments of flight and escape, are adapted in fiercer animals to the pursuit and prehension of their prey, and in this, and many other respects, their hand or 1 See Introduction to Entomology, ii. 310. Haltica oleracea, Nemorum, &c, 246 See Roget, B. T. i, 506. C. Stongyloceras. 3 Cervus. L. 5 Cervus Tarandus. foot is the part principally interesting. This is used for so many various purposes, that, perhaps, it will be best to take a summary survey, in this respect, of all the Classes of animals with articulated legs, and briefly point at their different structures and their uses. As I have already given an account of the two kinds of forceps of Crustaceans,1 I shall begin with the legs of the Arachnidans, or spiders. Every one who examines the web of a common spider, whether it is formed of concentric circles, supported by diverging rays, or whether it imitates any finely woven substance, will be convinced that she must be furnished with a peculiar set of organs to effect these purposes; that she must have something like a hand to work with. Amongst the small things that are wise upon earth, Solomon mentions the spider; and the way by which he tells us she shows her wisdom, is by her prehensory powers-she takes hold with her hands. And truly what Arachne does with her hands and her spinning organs is very wonderful, as I shall have occasion hereafter to show; I shall now only make a few observations upon the organs by which she takes hold. Spiders are gifted with the faculty of walking against gravity, even upon glass, and in a prone position. According to the observations of Mr. Blackwall, this is not effected by producing atmospheric pressure by the adhesion of suckers, but by a brush formed of "slender bristles, fringed on each side with exceeding fine hairs, gradually diminishing in length as they approach its extremity, where they occur in such profusion as to form a thick brush on its inferior surface.” These brushes he first discovered on a living specimen of the bird-spider, and the same structure, as far as his researches were carried, he found in those spiders which can walk against gravity and up glass. This is one of the modes by which they take hold with their hands, and thus they ascend walls, and set their snares in the palace as well as the cottage. Whoever examines the underside of the last joint or digit of the foot of this animal with a common pocket-lens, will see that it is clothed with a very thick brush, the hairs of which, under a more powerful magnifier, appear somewhat hooked at the apex; in some species this brush is divided longitudinally, so as to form two. But the organs that are more particularly connected with the weaving and structure of the snares of the spiders are most 1 See above, pp. 208, 209. 3 Blackwall in Linn. Trans. xvi. 481. t. xxxi. f. 5. 4 Mygale avicularia. 2 Prov. xxx. 28. worthy of attention. Setting aside the hunters1 and others. that weave no snares to entrap their prey, I shall consider those I intend to notice, under the usual names of weavers' and retiaries.3 Before Mr. Blackwall turned his attention to the proceedings of these ingenious and industrious animals, it had not been ascertained, in what respect their modes of spinning their webs, and the organs by which they formed their respective manufactures differed. But Mr. Blackwall, whose observations were principally made upon one of the weavers' which frequents the holes and cavities of walls, and similar places, observes that it spins a kind of web of differerent kinds of silk, the surface of which has a flocky appearance, from the web being as it were ravelled. This web is produced, he observes, by a double series of spines, opposed to each other, and planted on a prominent ridge of the upper side of the metatarsal joint, or that usually regarded as the first joint, of the foot of the posterior legs on the side next the abdomen. These spines are employed by the animal as a carding apparatus, the low series combing, as it were, or extracting, the ravelled web from the spinneret," and the upper series, by the insertion of its spines between those of the other, disengaging the web from them. By this curious operation, which it is not easy to describe clearly, the adhesive part of the snare is formed, thus large flies are casily caught and detained, which the animal, emerging from its concealment, soon despatches and devours. The organs by which the retiary spiders form their curious geometric snares have generally been described as three claws, the two uppermost armed with parallel teeth like a comb, and the lower one simple and often depressed; but Mr. Blackwall found, in a species related to the common garden spider," eight claws, seven of which had their lower side toothed. The object of this complex apparatus of claws simple and pectinated, is to enable these animals to take hold of any thread; to guide it; to pull it; to draw it out; to ascertain the nature of any thing ensnared, whether it be animate or inanimate; and to suspend itself. In fact the Creator has made their claws not only hands but eyes to these animals. 1 3 5 7 Aranea, venatoriæ, A. retiaria. Mammule. 2 A. textoria. 4 Clubiona atrox. Epeira Diadema. The species examined by Mr. B. was E. apoclisa. 8 Blackwall, ubi sup. 476. |