instinct urges them to pursue and devour. For this purpose their wings are admirably adapted not only by their volume, but by their power of contracting them, and giving them various inflections in flight, so that their speed is regulated by the object they are pursuing.

When we further reflect that their eyes are small and deepseated, we may conjecture that it requires extraordinary tact and delicacy of sensation in some other organs to supply this defect in its sight. Spallanzani found that blind bats fly as well as those that have eyes; that they avoided most expertly threads of fine silk which he had so stretched as just to leave room for them to pass between them: that they contracted, at will, their wings, if the threads were near, so as to avoid touching them; as well as when they passed between the branches. of trees; and also that they could suspend themselves in dark places, such as vaults, to the prominent angles. He deprived the same individuals of other organs of sensation, but they' were equally adroit in their flight, so that he concluded they must have some sensiferous organs different from those of other animals to enable them to thread the labyrinths through which they ordinarily pass.

Dr. Grant observes on this subject-"Bats are nocturnal, but, contrary to what is generally the case with nocturnal animals, their eyes are minute and feeble, and indeed, comparatively speaking, of minor importance, for so exquisite is the sense of feeling diffused over the surface of their membranous wings, that they are able to feel any vibration of air however imperceptible by us; they can tell, by the slight rebound of the air, whether they are flying near any wall, or opposing body, or in free space though their eyes be sealed or removed." A similar observation was long ago made by Mr. Bingley."

We see in the circumstances here detailed a remarkable instance of the Power, Wisdom, and Goodness of the Creator, in compensating for the absence or imperfection of one or more senses, by adding to the intensity of another, and in establishing its principal seat in organs so nicely adapted to derive most profit by the information communicated.

8

An animal nearly related to the vampyres, the cat-ape, commonly called the flying cat, and by some the flying dog, though nearly related to the bats, and included by Cuvier in the same Family, differs essentially from them, in being furnished with organs formed by the skin of the flanks connected with the

1 Quoted in Lit. Gaz. Feb. 9, 1834. 3 Galeopithecus.

2 Mem. of Brit. Quad. 34.

legs of each extremity, which are calculated for suspension rather than flight, being used, as Cuvier remarks, merely as a parachute, and thus belong to the second kind of wings, mentioned above. This animal, which climbs like a cat, vaults from one tree to another, by the aid of the above skin, which supports it in the air. The petaurists, or flying squirrels, and the phalangists, or flying oppossums are similarly equipped, and for a similar purpose. The common squirrel, using its tail as a rudder, leaps with great agility from tree to tree, without the said of this kind of parachute, the force of its spring being sufficient to counteract that of gravity. Providence has evidently added an organ of suspension, in the case of the three former animals, either because their vaults were necessarily longer, or because the greater weight of their bodies required it. The dreaded name of dragon, attached to the monsters of fable, has excited in our imagination ideas of beings clothed with unwonted terrors, from our earliest years, so that when we find the only animal that inherits their name is an insignificant lizard, not more than eight inches long, we are tempted to exclaim, Parturiunt montes. This little animal, under the name of wings, is furnished with two dorsal appendages independent of the legs, formed of the skin, and actually supported by the six first short ribs, which, instead of taking their usual curvature are extended in a right line. These organs are not used to fly with, but to support the animal in its leaps from branch to branch, and from tree to tree.

We sce in this instance, how exactly the means are adapted to the end proposed. This animal walks with difficulty, and consequently seldom descends from the trees. It is therefore enabled to move from one part of a tree to another, not by its legs, but by an organ formed out of its ribs! How various and singular in this instance, as well as in that of serpents, before alluded to, are the means adopted by a Being, who is never at a loss to answer the foreseen call of circumstances by wise expedients.

Steering Organs."-But wings are not the only organs of flight with which the Creator has fitted those animals, to which he has assigned the air as the theatre of their most striking and interesting locomotions. They would be like a ship at sea without a rudder, and be altogether at the mercy of every wind of heaven, had they no means to enable them to steer their vessel through the fluctuations of the viewless element assigned

1 Petaurus.

2 Phalangista. 4 See above, p. 258. 5 Gubernacula,

3 Sciurus vulgaris.

to them. The eagle and the vulture would be gifted in vain with the faculty of seeing objects at a great distance, had they no other organ than their sail-broad vans to direct them in their flight. The same remark will apply as well to the insect as to the bird, which would in vain endeavour to discharge its functions, unless it could steer its course according to the direction of its will and the information furnished by its senses. But upon examination, we shall find that God hath not left himself without witness in this department, but hath furnished every bird and insect with such an organ of steerage as the case of each required; nay, even amongst the beasts and the reptiles we may discover similar means of directing their motions, especially when they leap, whether from the ground, or from tree to tree.

The caudal fin, or tail of fishes, may be regarded as belonging in some degree to this head; but as this is also their principal organ of locomotion, I thought it best to consider it with the other fins.

The abdomen of many insects seems to serve them as à rudder, being composed of several inosculating, rings formed each of a dorsal and ventral segment; it is capable of considerable flexion in almost all directions; it can be elevated or depressed, and turned to either side, so that it seems, in a great degree calcu lated to enable insects to change the course of their flight according to their will. But besides this important organwhich by the air it is constantly inspiring adds force also to the internal impulse, and to the air-vessels in the wings-insects have other auxiliaries to keep them in their right course. Whoever has seen any grasshopper take flight, or leap from the ground, will find that they stretch out their hind legs, and, like certain birds, use them as a rudder. The tails also of the day-flies1 seem to be used by them as a kind of balancer in their choral dances up and down in the sun's declining beam. But the most interesting and beautiful organ for steering animals in the air, is that formed by the tail feathers of birds, called by ornithologists, rectrices, or governing feathers, because they are used to direct their course; these are feathers planted in the rump, usually twelve in number-but in some amounting to nearly twenty-constituting two sets of feathers of six each, and forming together a kind of fork like the caudal fin of some fishes; the inside of each feather is set with much larger plumelets than the outside, so that there is a double series of corresponding feathers beginning one on the right side, and the

1 Ephemera.

2 Uropygium.

other on the left; the middle feathers in each series differ sometimes from the five exterior ones, being more acute, and wearing a different aspect. In flight the tail-feathers appear to be expanded, and probably the bird, by giving an impulse to either series, can turn this way or that; or by their depression or elevation, judging from their analogy with the caudal fin of fishes, rise or fall. The rudder-tail here described is that of the male bull-finch; in many birds of the Gallinaceous Order, as the common cock and peacock, these feathers form a glori ous ornament, but scem to lose their use as a steering appara tus. In the black game the two sets of feathers of the tail turn outwards, one on eack side, and so form a fork; and, in our domestic poultry, these sets of feathers, when not expanded, fold upon each other. Some of the waders, the tail-feathers of which are short, use their long legs like the grasshoppers, as a rudder in flight, stretched out strait behind them.

4

3

Many of the web-footed birds, as the goose and duck tribes, also have these feathers very short, which seems a convenient provision for aquatic birds, but whether their legs assist in directing their course seems not to have been ascertained. Some of them, however, as the pin-tail ducks have the middle. feathers of the tail elongated, as they are in many other birds; in the swallow tribe," and the sea-swallow, the external feathers of the tail are elongated, as these birds are frequently turning when in the air and flying backwards and forwards: their Creator has thus equipped them for their ever changing evolutions. Some birds, as the thrushes," magpies, and other crows, have all the tail feathers long, which gives great power to them in flight.

The tails of quadrupeds, both oviparous and viviparous. appear, in many cases, to act in some degree as a rudder. They are not only useful to those lately mentioned, that by the assistance of a kind of parachute, leap from tree to tree; but likewise to the feline race, when they spring upon their prey; the tail is then extended stiffly in a right line, as if to guide them through the air straight to the object they have been watching from their lair. The long tail also of many lizards may in their sinuous windings, serve some purpose connected with their locomotion related to the one under discussion, though we have not data sufficient to speak positively on the subject.

Legs. We are now arrived at organs that are the most perfect instruments of locomotion and prehension, organs which are found in their greatest perfection in the highest animals, articulated legs and arms, terminating in the most perfect instrument, upon the due employment or misemployment of which the weal or wo of the whole human race, as far as second causes are concerned, depend.

The legs of animals may be considered generally as to their number, composition, and adaptation to their functions.

As to their number, taking the legs of vertebrated animals, which may be regarded, being the most perfect, as a standard to measure others by, we may assume that four is the most perfect number. Thus, in man, the highest animal, there are two for locomotion, and two principally for prehension. Taking, therefore, man for the ultimate point to which all tend, let us see how, in this respect, the scale is formed.

We observed in certain tribes of the Annelidans, an approach to jointed legs, and it should seem a link, connecting, in some degree, that Class with the Myriapods; with these last, therefore, me may start in our consideration of articulated locomotive organs, and here we find a long body moved by numerous legs, gradually acquired, as we have seen, with its increasing length. We may observe, that in the superior tribes of animals, the four legs being planted in pairs at each extremity of the body, the gradual increase of stature did not require additional props, but only the proportionate growth of the existing or natal legs and arms; but in the Myriapods, where the great increase of the body in length is not between the original extremities, but beyond them, additional supports were requisite, so that as the body increased in length, its Creator, in his goodness willed— that it might not draw its slow length along like a wounded snake-that it should be furnished at the same time with a proportionate increase in the number of its locomotive organs. These animals, then, with respect to number of legs, may be regarded as at the foot of the scale, and are the farthest removed from man.

From the Myriapods we go to the great Crustacean host, in which, including the maxillary legs, the real analogue of the legs of Hexapods, the typical number is sixteen; and from these, the transition is naturally to the spiders, which have half that number, and from them to the insect tribes, walking only upon six legs. Having arrived at a hexapod type, we may observe that one pair of the legs has a direction towards the head, and are located in the anterior segment of the trunk; and that the other two pairs have a direction the contrary way, towards the ab