556 Studies in the Theory of Descent. 



possible to reply to the main question, viz. 

 whether this metamorphosis was determined by 

 external conditions or by purely internal causes ; 

 to say nothing of the possibility of there perhaps 

 being discoverable certain definite external in- 

 fluences by means of which the metamorphosis 

 could have been induced with certainty. But 

 while these points are undecided all attempted 

 theoretical interpretations of the phenomenon 

 must be devoid of a solid basis. 



It appeared to me from the first that the history 

 of this transformation of the Axolotl was of 

 special theoretical value ; indeed I believed that 

 it might possibly furnish a special case for de- 

 ciding the truth of those ground-principles, 

 according to which the origin of this species is 

 represented by the two conflicting schools as a 

 case of transformation or as one of heterogenesis. 

 I therefore determined to make some experiments 

 with the Axolotl myself, in the hopes of being 

 fortunate enough to be able to throw some light 

 upon the subject. 



In the year 1872 Prof. v. Kolliker was so good 

 as to leave with me five specimens of his Axolotls, 

 bred in Wiirzburg, and these furnished a numerous 

 progeny in the following year. With these I 

 carried out the idea, the theoretical bearing of 

 which will be shown subsequently, whether it 

 would not be possible to force all the larvae, or 

 at any rate, the greater majority, to undergo 



