and its Natural Affinities. 365 
“ Recueil d’Observations de Zoologie et d’Anatomie comparée ” 
of the Voyage of Humboldt and Bonpland*. The title of this 
memoir gave occasion to naturalists to make use of the term 
“doubtful reptiles” to indicate this group. That which was 
then doubtful is not so, however, at the present day. Doubts 
there will always be: what field of human research is free from 
them? but these doubts at present affect other points. That 
which was then unascertained, and which Cuvier sought to de- 
termine, was whether the reptiles with branchiz were not larvee 
destined to lose those organs. He examined the Axolotl, of 
which Humboldt had given him two specimens which he had 
brought from Mexico, and he compared it with the Siren of 
South Carolina and the Proteus of the lakes and subterranean 
waters of Carniola and Dalmatia. All these animals possessed 
branchiz and lungs. 
As the result of his researches, Cuvier was convinced that the 
Siren and the Proteus were adult animals, always retaining the 
double organs of respiration}, while he regarded the Axolotl as 
the larval state of some large unknown Salamander}. Sub- 
sequently, however, he placed the Axolotl among the genera 
with permanent branchiz, along with Proteus and Siren§. 
To these three species, which form as many genera, we must 
now add some others, coming, like the Siren and Axolotl, from 
North America. But, besides these genera with persistent ¢ gills, 
we cannot refuse a place i in this natural group for certain animals 
very similar, but in which we find no gills, although there is a 
branchial orifice on either side of the neck. A large reptile of 
this division was already known to Cuvier when he published 
* I., Paris, 1811, pp. 93-126: “Recherches anatomiques sur les Rep- 
tiles regardés encore comme douteux par les naturalistes, faites a occasion 
de Axolotl rapporté par M. de Humboldt du Mexique.”’ This was read 
at the Institut National, January 19 & 26, 1807. 
+ Prof. B. Smith Barton had mdependently arrived at the same convic- 
tion.—‘ Some Account of the Siren lacertina’ (Philadelphia, 1807), abrochure 
in the form of a letter to J. G. Schneider, and of which only fifty copies 
were printed, one of which I obtained at the sale of Blumenbach’s library. 
{ Loe. cit. p. 116. This was still the opinion of Cuvier when he pub- 
habe the first edition of his ‘Régne Animal’ (1817, 1 ii. pe bon): 
§ Regne Animal, 2nd ed. 18 27, i. p- 119, note: “So many persons 
affirm that it does not lose them, that I feel obliged to acquiesce.” How- 
ever, more recently still, the distinguished American, Spencer Baird, re- 
tained similar doubts (Journ. Acad. Nat. Se. of Philadelphia, Oct. 1849, 
vol. i. ser. 2. p. 281, “ Revision of the North American Tailed Batrachia’’). 
The author expresses himself as follows :—“ It is only because there is no 
positive proof to the contrary that I retain the genus Siredon as real, 
placing it at the bottom of the series. It so much resembles the larva of 
Ambystoma punctata, in both external form and internal structure, that I 
ane a. believe it to be the larva of some gigantic species of this genus” 
p. 292), 
