REPTILIA. 201 
in the larva, are very long. Before the forelegs become completely 
formed, those behind sprout out in a similar manner, with first three, then 
four, and finally five toes. During this time the gills have increased in the 
number of branches, and finally exhibit a beautiful arborescent appearance, 
in which the circulation of the blood can be distinctly seen by means of a 
simple lens. At the time, then, that the individual has attained its perfect 
larval state, it has four legs, with four fingers on the anterior, and five on 
the posterior ; the jaws are wide, the mouth well provided with teeth; the 
superior maxillary bones, however, not developed, and the pterygoid bone 
with card teeth, asin Proteus, Menobranchus, and Siren. The animal 
presents a perfect fac-simile of the Mexican axolotl, which, although by 
many naturalists considered to be a permanent form, is, in all probability, 
only a larval state of some very large species of salamander. Our animal 
is now exceedingly voracious, devouring tadpoles, and weaker larve of its 
own species, with great avidity. Its entire food, in fact, has consisted 
throughout of animal matter in some form or other. ‘This state of things, 
in all probability, continues from one spring to the next, or for nearly a 
year: at the expiration of which time the gills will be seen to wither 
gradually away, the lateral holes in the neck to grow together, and all 
these traces of larval life finally to disappear. The superior maxillary 
becomes developed and ossified, the temporary teeth in the roof of the 
mouth vanish, the lungs acquire a great development, yellow spots break 
out of the dark ground of the body, and finally the animal leaves the water, 
never to return to it again except for a short period in the spring of the 
year, when it is engaged in the function of reproduction. Such is a brief 
outline of these changes, which vary in different genera and species. 
Proceeding now to the more particular consideration of the Batrachiu 
urodela, we commence, first, with the sub-order Tvrematodera. Here we 
find that the apertures in the side of the neck remain open throughout life, 
and in several genera even the gills are persistent. The first genus that 
would come properly here is that of Siredon, or the Axolotl, whose distin- 
guishing characteristic is to be found in the opercular flap being detached 
from the subjacent integuments, and continuous across the throat. The 
gills and gill-openings are very highly developed, the tail strongly com- 
pressed, and provided with a well developed fin. Toes, four in front, five 
behind, all muck elongated. ‘Two species have been described, the one S. 
mexicanus, from the lakes in the vicinity of the city of Mexico, the other 
S. maculaius, from the New Mexican Rio Grande. For reasons above 
mentioned, we prefer to consider them as larvee, and proceed to the 
consideration of the genus Proteus. The single species of this genus, 
P. anguinus, has long been an object of great interest to naturalists, on 
account of its individual features, as well as the circumstances under 
which it is found. It is an inhabitant of the subterranean waters of 
Sittich in Lower Carniola, and of the great cave of Adelsburg on the main 
road from Trieste to Vienna. Occasionally it has been caught in the 
external outlets of these waters, but, like the blind fish of the Mammoth 
Cave of Kentucky, its usual residence is at a distance of some miles from 
455 
