ON THE CHANGE OF THE MEXICAN AXOLOTL TO AN AMBLY- 



STOMA. 



By Dr. August Weissiann, Professor at Frelhurg, Breisgau. 

 [Translated by Henry M. Douglass, Champaign, III.] 



Since Dameril first announced tbe change of a nnmber of Axolotls 

 into the so-cailed Amblystoma form, this Mexican fish-salamander has 

 been bred in aquariums at many European places, principally with a 

 view to determine the conditions under which that change occurs, and 

 then from that to draw further conclusions upon the real causes of this 

 exceptional and therefore so mysterious metamorphosis. 



The creatures were easily propagated everywhere, and that in great 

 numbers. Yet not only did the cases in which the transformation 

 occurred remain exceedingly rare, but no one succeeded in answering 

 the first and most important question, whether this was called forth by 

 external circumstances or was dependent upon purely intrinsic causes. 

 Much less were any definite external influences found through whose 

 presence one could bring on the metamorphosis with certainty. 



But until this point is decided, all attempts at theoretical interpre- 

 tation and use of the phenomenon must remain without any firm found- 

 ation. 



To me this history of the Axolotl's transformation always seemed to 

 be of quite a particular interest. I believed, indeed, that possibly this 

 one special case might be suflicient to determine the correctness of the 

 fundamental principles, according to which the origin of species is repre- 

 sented in the two hostile camps of development and heterogeneous or dis- 

 tinct creation. So I resolved to set about experiments with the Axolotl 

 myself, in the hope that perhaps it would be my good fortune to throw 

 some light upon this subject. 



In the year 1872, Herr von KoUiker had the kindness to i^resent to 

 me five of the Axolotls he had bred in Wiirzburg. In the following 

 year these produced an abundant brood. With them I tried to settle 

 the question, whether it was not possible to force all the larvse to the 

 change, or at least the greater part, if they were brought into circum- 

 stances which rendered the use of the gills difiicult, that of the lungs 

 easy. This, in other words, would be to comi^el them from a certain age 

 to live half on the land. It will be seen further on, what theoretical 

 grounds led me to this idea. 



Meanwhile I reached no results that year. The most of the larvae 

 died before the time for such experiments seemed to have come. The 



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