The Transformation of the Mexican Axolot I. 583 



be shown that this artificially produced change is 

 only apparently an abrupt transformation, and is 

 actually a reversion to the much older winter 

 form ; so here we have not an actual, but only an 

 apparent remodelling of the species a reversion 

 to the phyletically older form. 



This certainly appears a paradox, inasmuch as 

 a form here arises by reversion which must yet 

 undoubtedly rank as the more highly developed. 

 I believe, however, that much which seems para- 

 doxical in this statement will disappear on further 

 examination. 



It must in the first place be taken into con- 

 sideration that the phyletic development of species 

 need not by any means always take place by 

 advancement. We have indeed many cases of 

 retrogressive development, although in a some- 

 what different sense, as with parasites and those 

 forms which have degenerated from free loco- 

 motion to a sedentary mode of life." I do not 

 confuse this kind of retrogressive development, 

 arising from the arrest of certain organs and 



" [This is the principle of " Degeneration " recognized by 

 Darwin (see " Origin of Species," 6th ed. p. 389, and " Descent 

 of Man," vol. i. p. 206), and given fuller expression to by 

 Dr. Anton Dohrn (see his work entitled " Der Ursprung der 

 Wirbelthiere und das Princip des Functionswechsels." Leipzig, 

 1875). A large number of cases have been brought together 

 by Prof. E. R. Lankester, in his recent interesting work on 

 " Degeneration, a Chapter in Darwinism." Nature series, 1 880. 

 R.M.] 



