frog and newt changes, by a wonderful transition, from that of a fish to that of a perfect reptile; while in the proteus and its allies, it continues to be that of the fish, with the addition of a modified state of pulmonary circulation, approaching that of the perfect reptile structure. As our aim is not to enter into minute anatomical details, we shall not pursue this subject: to have omitted all notice of it, however, would have been unpardonable. It is in these curious and interesting phenomena, that we behold exemplified so clearly and forcibly the "wisdom of God in creation." Here the atheist is at once confounded, while the man of science and piety recognizes with pure delight the power and superintending care of Him, who made "every creeping thing," and who has laid his works before us, that while we admire them, we may glorify his name. Reptiles have either four limbs, two, or none; the ribs are sometimes very numerous, sometimes wanting; there is no true distinction between the chest and abdomen, no diaphragm or muscular expansion, dividing, as in quadrupeds, these two cavities. As the blood is of a low temperature, these animals need neither fur nor feathers, for the retension of the vital heat: they are therefore covered either with horny plates, or with scales, or have the skin entirely naked. They possess the senses of hearing, sight, taste, smell, and touch. Their sight is in general extremely acute; for on this sense depends their pursuit of food, and their perception of the approach of enemies. In some few, however, as the proteus, which inhabits subterraneous waters, the eye is extremely minute, appearing like a black dot, covered by the transparent skin, and is in a rudimentary condition. The senses of taste, smell, and touch in reptiles are comparatively feeble. With regard to hearing, there appears to be considerable variation in different groups. In serpents, this sense is very acute, and these animals evidently derive pleasure from musical notes, as is well known to the serpent charmers of the east. In lizards, also, the sense of hearing appears to be quick; but in tortoises and in the amphibia, it is probably much more obtuse. In most cases, the internal organs of hearing are entirely covered by the scaly investment of the head, or by the naked skin: in lizards generally, the tympanic or drumlike membrane is stretched over the external orifice of the ear, and is on a level with the scaly covering of the rest of the head; but in the crocodile, the external orifice, instead of being thus permanently closed, is provided with a firm, hard, movable lid, or operculum, by means of which the aperture may be either stopped or kept open. Thus while basking on the margin of the river, or lying there in ambush for prey, the crocodile has the power of raising the earlid, in order to listen attentively to every noise; but when he dives beneath the water, either for safety, or to drown the victim he has seized, the entrance of water into the auditory cavities is prevented by the firm shutting of the lid, which accurately fits the orifice. Reptiles are ordinarily oviparous: they bury their eggs in the sand, deposit them in warm places of concealment, or leave them floating on the water, exposed to the rays of the sun: in due time, the young are hatched. In some few instances, the eggs are hatched immediately previous to their exclusion, as in the case of the viper, and the young are taken under the mother's protection. * By way of review, we may thus recapitulate, in a succinct manner, the above remarks, and at the same time give in brief the general characters of the present class. Reptiles are cold and red-blooded vertebrate animals, with a heart consisting essentially of two auricles and one ventricle: there are always true lungs, but in one tribe, the amphibia, which commence their active state of existence as aquatic beings in the form of a fish, there are also gills, which mostly perish as the lungs develope, but not always; some groups having permanent gills, as well as lungs: all are oviparous. The bodies of the reptilia * Ovum; an egg; paro, to produce. are either covered with horny plates or scales, spires, or granules; or, as in the ordinary amphibia, with a skin entirely naked. There is either no external organ of hearing, or only a simple orifice, open in some, in others. covered by a transparent tympanic membrane; and in a few, with a moveable valve. The number of the limbs never exceeds four; some groups are destitute of limbs, the ribs greatly assisting in terrestrial locomotion. Most reptiles are carnivorous: some, however, (and these belong to the first group, namely, the tortoises,) are vegetable feeders; a few feed both on small animals, as slugs, insects, etc., and on leaves and fruits. An extensive division of one order presents us with creatures formidable from the possession of poison fangs, death rapidly following their bite. We shall divide the reptilia into the following orders :- II. Sauria-Crocodiles, Lizards, etc., (apos, III. Ophidia-Snakes, (Opis, ophis, a snake.) These orders are well defined; nevertheless, they pass into each other by certain gradations of form, which, indeed, are more evidently traceable between two of the orders, namely, Sauria and Ophidia, than between these and the two others, but which are still to be recognised even here. Of the Chelonia, or tortoises, for example, the serpentine water-tortoise, Emysaurus serpentinus, Bibr. (Chelydra lacertina, Schweigg.) seems to approach the Saurian order in many particulars; or rather, perhaps, the extinct group, termed Enaliosaurians by Conybeare, in which are included the gigantic fossil reptiles, the ichthyosauri and plesiosauri; and which • Evalios, (enalios,) marine; oaupos, (sauros,) a lizard. * probably constituted a link intermediate between the tortoises and crocodiles. The Saurian order passes, by very marked steps, into that of the snakes; the genera Scincus, Seps, Bipes, Pygopus, and others, on the part of the former, merging into the genera Pseudopus, Ophisaurus, and Anguis, (slow-worm,) on the part of the latter; and thus, by gentle transitions, are the snakes and lizards united. The passage from the snakes to the Amphibia is less distinct. Perhaps, however, an intermediate link may be found in the genus Cæcilia. This genus Cuvier retains within the pale of the Ophidia; but observes, that many naturalists consider it as belonging to the Amphibia, (Batraciens,)" although we know not whether it undergoes a metamorphosis, or the contrary." If Müller be correct, however, it would seem that there are branchiæ at an early period, which are ultimately lost. With the elongated form of a snake, the animals of this singular genus, Cæcilia, have the skin smooth, viscous, and marked with a series of annular or ring-like depressions. It appears to be naked, but on a careful examination minute scales are found in its substance, and disposed between its folds in regular rows. eyes are very small, almost concealed beneath the skin, and in one instance (Cæcilia lumbricoides, or the wormlike Cæcilia) they are wanting. It is from the rudimentary condition of the eyes, that the genus derives its name, cæcus, in Latin meaning blind. The form of the head is depressed, the ribs are too short to encircle the body, as they do in snakes generally; and what is still more remarkable, the vertebræ are articulated to each other by facets, hollowed out and filled with a gelatinous cartilage, as in fishes, and some of the lowest of the amphibious order. The skull is joined to the first vertebra by two condyles; whereas, in serpents it is joined by one only. Professor Bell, who considers the Amphibia to form a distinct class from the Reptilia, gives the Cæcilia as the example of an order termed Apoda, and which concludes the series of the Amphibia; and, in like The manner, Dr. Fleming closes with the Cæcilia, the batrachian section of the reptiles; observing, that the absence of scales, the cup-shaped vertebræ, the shortness of the ribs, and the simplicity of the heart, intimate that this genus should not, as heretofore, be included among the serpents. If the existence of branchiæ, or gills, in the Cæcilia, at an early period of life be, as Müller asserts, the fact, we have at once positive grounds for regarding it as forming part of the Amphibia; while, perhaps, it links these with the Ophidia, or serpents. The passage of the Amphibia into the fishes is very palpable. It is interesting to see by what insensible gradations the former merge into the latter, through the amphiuma, the axolotl, the menobranchus, the proteus, the siren, and the lepidosiren. The animals of the latter genus, of which two species are known, one a native of the Amazon, (L. paradoxa,) the other of the Gambia, (L. annectans,) are so intermediate in form and structure between a reptile and a fish, though they possess lungs as well as branchiæ, that it is difficult to know where to place them. Dr. Natterer regards them as Amphibia; Professor Owen as fishes, on the grounds that the characters of the latter predominate. The engraving of Lepidosiren annectans, will serve to illustrate the justice of our observations. The transitions, by regular gradations, from group to group, which the naturalist continually meets with in his investigations of nature, afford pleasing proofs of the harmony and order of the plan of creation; they betoken the oneness of a great scheme, wisely arranged, and of which the parts link all together, and thus they demonstrate that nothing came into being by that kind of chance, that fortuitous concurrence of circumstances, that assumption of organization by matter previously inert, which those writers suppose, who contend for the baseless theory of spontaneous or equivocal productions. Granting that laws tending to such a production were, |