580 Studies in the Theory of Descent. 



the arched branchial apparatus, the palatine teeth, 

 the skin, &c., of the Axolotl. 



These facts prove, therefore, that the shedding 

 of the gills by no means always entails all the 

 other modifications which we observe in the meta- 

 morphosis of Axolotl, so that these modifications 

 are thus not by any means the necessary and 

 immediate consequence of such gill shedding. 



Whether these modifications will occur after a 

 long series of generations whether the successors 

 of Cryptobranchus will also one day acquire the 

 salamandriform structure is another question, and 

 one which I could not exactly answer in the 

 negative. But this question does not here come 

 into consideration, as we are now only concerned 

 with the immediate result of the shedding of the 

 gills. 



The problem appears therefore to be as fol- 

 lows : Either the hitherto received interpretation 

 of the transformational history of the Axolotl as a 

 further development of the species is incorrect, or 

 else the case of Axolotl incontestably proves the 

 existence of a phyletic vital force. 



We have now to ask whether the facts of this 

 transformational history are not capable of another 

 explanation. 



I believe that this is certainly possible, and that 

 another interpretation can be shown to be correct 

 with some degree of probability. 



I am of opinion that those Amblystomas which 



