ON CHANGE OF MEXICAN AXOLOTL TO AN AMBLYSTOMA. 353 



For Nos. II., III., and lY., on the other hand, such a supposition has bnt 

 little probability. All three larvaB sought to keep themselves in deeper 

 water, avoided as long: as possible the shallow places which compelled 

 them to mere lung-breathing, and only completed the change more than 

 a mouth later. 



With No. v., moreover, it can scarcely appear doubtful that it would 

 not have made the change without the forcible habituation to abode in 

 the air. 



From these results may well be drawn the conclusion, most Axolotl 

 larvse change to the Amblystoma form if at the age of six to nine 

 months they are brought into water so shallow that they must chiefly 

 breathe with the lungs. The experiments iu question are small in num- 

 ber, to be sure, but such a conclusion cannot be called hasty, when it is 

 considered that Dum6ril, among many hundreds (the number is not 

 given precisely) of Axolotls, obtained only some thirty Amblystomas; 

 that likewise, among several hundred Axolotls, von Kolliker bred only a 

 single Amblystoma. 



It only remains doubtful whether every larva can be compelled to make 

 the change, and this question can only be determined by new experiments. 

 It had been my intention to defer the publication of those above given 

 until they were repeated in greater fullness by Miss von Chauvin. But 

 as my Axolotls have given me no young this year (1875), I had to give 

 that up for the time, and could do this the more willingly, since it is 

 rather irrelevant to the theoretical interest of the facts whether all or 

 only almost all of the Axolotls may be forced to make the transforma- 

 tion. On the other hand, I will not forbear to mention, that the curator 

 of the zoological museum here, Herr Gehrig, reared a considerable num- 

 ber of larvae from the same brood, with which Miss von Chauvin experi- 

 mented, and that of these larvae six passed through the winter tcithout 

 undergoing the transformation. They were always kept iu deep water, 

 and therefore constituted the counter-experiment to those communicated 

 above, showing that this whole brood by no means possessed a preilis- 

 position to undergo the transformation. 



If, now, these new facts are to be made use of to clear up our conception 

 of the nature of this unusual process of transformation, we must, before 

 all else, bring to our aid the data already known. 



In the first place, it is to be laid down that Siredon Mexicanus, in its hornet 

 so far as toe Tcnow, never undergoes the transformation. From that locality 

 it is Jcnoicn only in the Siredon form. The testimony which I find on this 

 point comes from De Saussure, * who himself observed the Axolotl in 

 the Mexican waters. This naturalist has uever seen even a single Am- 

 blystoma in the vicinity of the lakes, and "yet the larvae of the Axolotl 

 are so common there, that they are brought into market by thousands." 

 De Saussure believes that the Axolotl does not make the change in 

 Mexico. 



* Verhandl. d. Scliwoiz. Naturforsch. Gesellschaft. Einsiedeln, 1S68. 

 23 S 



