The Transformation of the Mexican Axolot I. 605 



which are only to be found in few species. One 

 might certainly attempt to apply these facts in a 

 quite opposite sense, and to regard them as 

 unfavourable to my theory, since the retreat of the 

 water from a great portion of the bottom of the 

 lake would so one might think rather facilitate 

 transition to a life upon land, and indeed compel 

 the adoption of such a mode of existence. But 

 we should thus forget that the exposed bottom of 

 the lake is a sterile surface without food or place 

 of concealment, and, above all, without vegetation ; 

 and further, that owing to the considerable saline- 

 ness of the water (specific gravity = 1.0215)," the 

 whole of the exposed surface must be incrusted 

 with salt, a circumstance which would render it 

 quite impossible for the creatures to feed upon 

 land. Sodic chloride and carbonate are dissolved 

 in the water in such considerable quantities, that 

 they are regularly deposited upon the shores of 

 the lake as a crust, which is collected during the 

 dry season of the year and sent into the market 

 under the name of " tequisquite " (Miihlenpfordt)." 

 Thus the supposition is not wanting in support, 

 that peculiar conditions make it more difficult for 

 the creature to obtain its food upon land than in 



" [The specific gravity of sea water (Atlantic), according to 

 the determinations of Mr. Buchanan on board the "Chal- 

 lenger," at 15.56 C. varies from 1.0278 to 1.0240. That of 

 the water of the Dead Sea is 1.17205. Watts' "Diet, of 

 Chemistry," vol. v., table, p. 1017. R.M.] 



" Loc. cit. p. 252. 



R r 2 



