The Transformation of the Mexican Axolotl. 593 



or if we were able to induce the majority of the 

 individuals of this brood to become metamorphosed 

 into Tritons by keeping them in shallow water ? 

 According to my view this is precisely the case of 

 the Mexican Axolotl. 



I need not, however, restrict myself to this in 

 order to support my hypothesis, but must also 

 directly combat the view hitherto received, since 

 the latter is in contradiction with facts. 



Did there really exist in the Axolotl a tendency 

 to sudden phyletic advancement, then one fact 

 would remain quite incomprehensible, viz. the 

 sterility of the Amblystomas. 



Out of about thirty Amblystomas obtained by 

 Dumeril down to the year 1870, there was not one 

 in a state of sexual maturity ; neither copulation 

 nor deposition of eggs took place, and the anatomi- 

 cal investigation of single specimens showed that 

 the eggs were immature, and that the spermatozoa, 

 although present, were without the undulating mem- 

 brane characteristic of the salamanders, but were 

 not devoid of all power of movement, only, as estab- 

 lished by Quatref ages, were "incompletely motile." 3 



So also the five Amblystomas about which I 

 have been writing, show up to the present time no 

 appearance of reproduction. 



The objection raised by Sacc," that the sterility 



10 CompL Rend. voL v. 1870, p. 70. 

 " Bull. Soc. NeuchuteL vol. viii. p. 192. Referenc given 

 in "Troschel's Jahresbericht " for 1869. 



