S6 Observations on the Natural History 



open into the mouth. This circumstance prompted us to exisi- 

 niine the condition of the bones of the face in these larvae, and 

 Ave liave tliereby satisfied ourselves that the larva of the sala^- 

 niander is unable to breathe by lungs, until the maxillary bones, 

 the zygomatic arches, and the palatine bones are sufficiently 

 developed to fornt the canal of the nostrils, in such a manner 

 timt its posteiior extremity may open into the mouth. Before 

 this canal is so formed, these larvse are unable to respire atmo- 

 spheric air, and, if taken out of the water, they then soon die ; 

 and, therefore, guided by analogy, we incline to the belief, that, 

 to the siren, whose nostrils " ne perietrent point dans la bouche,"^ 

 the same things ought to happen. Moreover,, as its lungs are 

 similar in all respects to tliose of the salamander, and are fur- 

 nished with a tiue glottis, we are farther of opinion, that the 

 siren is the larva of some reptile, the genus of which is as yet 

 unknown, and which will differ from ks larva in not possessing 

 gills, and in having a trunk somewhat longer. 



To return to the proteus.— We consider that it is not an am- 

 phibious animalj having a double circulation, as some have 

 maintained, but a perfect reptile, different entirely from all 

 others. It is a reptile, in respect to its having a single circula- 

 tion, and a fish, in regard to its mode of respiration, — in other 

 words, it is a reptile which respires air mixed with water, while 

 others reispire atmospheric air : so that, were it allowable to re- 

 vive the old idea of a chain of beings, the proteus might be 

 regarded as the link which would connect reptiles with fishes. 



From the facts and circumstances above stated, it appears, 

 that the proteus is an animal, which, like fishes, is capable of, 

 respiring only in water. Its branchial circulation, however,, 

 is only a fraction of the greater circulation, whence it follows, 

 that, in respiration, it consumes less oxygen than fishes do ; 

 and, consequently, a smaller quantity of blood in a given time 

 is changed in the gills of the proteus, than, in like circumstances, 

 is changed in the gills of fishes. From this circumstance, as 

 appears to us, continue the authors, arise the inertness, the 

 slow growth, the capacity of enduring fasting, the indisposition 

 in the blood to coagulate, and, lastly, the power of living in a 

 stagnant water, where a fish of equal size would die. With re- 

 gard to the faculty of generating heat, the authors are unable 



