as complete as the others." Cuvier further observes that whilst the branchia subsist, the aorta, in coming from the heart, is divided into as many branches on each side as there are branchia. The blood of the branchia returns by the veins, which unite towards the back in a single arterial trunk, as in the fishes; it is from this trunk, or immediately from the veins which form it, that the greatest part of the arteries which nourish the body, and even those which conduct the blood for respiration in the lung, spring. But

SKELETON OF SIREN.

in the species which lose their branchiæ naturally, the branches which go there become obliterated, except two which unite in a dorsal artery, and of which each gives off a small branch to the lung. "It is," adds this eminent comparative anatomist, "the circulation of a fish metamorphosed into the circulation of a reptile."

The same author observes that it had been objected that it would be impossible for these

animals to respire air without ribs or diaphragm, and without the power possessed by the tortoises and frogs to cause it to enter by the nostrils, in order that, so to speak, it might be swallowed, because the nostrils of the Sirens do not lead into the mouth, and the branchial apertures must let it escape. But his own observations, made upon well-preserved individuals, showed Cuvier that the nostrils in the Siren do communicate with the mouth by a hole pierced as in the Proteus, between the lip and the palatal bone which carries the teeth. The membranous opercula of their branchiæ are muscular internally, and capable of hermetically sealing the apertures; then it is very easy for the Siren, by dilating its throat, to introduce the air into the mouth, and to force it afterwards, by contracting the throat, into its larynx. Even without this structure of the nostrils, the animal could produce the same effect by opening its lips a little: a theory which Cuvier applies to the Proteus as well as the Siren.

on

Professor Owen has contributed some interesting observations to the Penny Cyclopædia,* the size of the blood-disks (commonly called globules) in the Amphibia as compared with other animals. Their size in these Reptiles is very great, and their magnitude seems to bear a proportion to the permanency of the external gills, or branchia. În the double-breathing animals before us, the Sirens and Protei, these disks are so large as to be distinguishable even with the unassisted eye, while their appearance under a microscope is exhibited in the accompanying

figures. The large oval figures exhibit their form as seen directly and sideways; the smaller ones represent the human blood-disk for the purpose of comparison; both are magnified seven hundred times in linear dimensions. The blood from which the former figures were taken was

obtained from one of the external gills of a Siren lacertina twenty inches in length, which was then (1841) living at the Zoological Gardens, Regent's Park. Though subjected to examination immediately, the large figure shows, in the crossing lines, traces of folds produced by the partial drying of the external capsule.

The species contained in this Order are very few, and compose but a single Family, Proteida; they are rather large animals, of dull sluggish manners, much resembling eels in form, with minute rudimentary feet, inhabiting the mud of

lakes, in America and Europe. They subsist on worms, and probably other soft-bodied animals, which they find in the mud or water.

GENUS PROTEUS (LAUR.).

In this genus, which, from the singularity of its structure and appearance, and still more from the anomalous character of the

situation in which it is found, has excited great interest among zoologists, there are four short limbs, each pair greatly separated from the other, of which the fore feet have three toes, and the hind only two: the tail is vertically compressed, so as to form a swimming organ; the muzzle is lengthened and depressed; both jaws are furnished with minute teeth; the tongue is but slightly moveable, free at the anterior part: the eyes are excessively small and concealed beneath the skin of the head: the ear-drum is also concealed. The skeleton has considerable resemblance to that of the Salamanders, but the conformation of the skull is different; and the vertebræ are much more numerous, while the rudimentary ribs are fewer. The skin is smooth, viscid, and colourless. The branchiæ project from each side of the neck in the form of tufts, of a crimson hue.

SKULL OF PROTEUS.

The European Proteus (Proteus anguinus, LAUR.) is much like an eel with minute feet, and is one of the most interesting links in the chain of animated nature, connecting the Reptiles with the Fishes. The deep and dark subterranean lakes of Austria are the only locality in which this singular creature has yet been discovered. One of the most romantic and

splendid caverns in Europe is the Grotto of the Magdalene, near Adelsburg, in the duchy of Carniola. The whole of that region consists of bold craggy rocks and mountains of limestone formation, perforated with spacious branching caverns, in whose awful recesses sleep the