Preface to the English Edition. xxv 



were necessary for drawing certain general con- 

 clusions. It would indeed be most interesting to 

 extend such observations to other groups of 

 Lepidoptera. 



The third essay also, for similar reasons, is 

 based essentially upon the same materials, viz. 

 the Lepidoptera. It is therein attempted to 

 approach the general problem does there or 

 does theje not exist an internal transforming 

 force ? from a quite different and, I may say, 

 opposite point of view. The form-relationships 

 of Lepidoptera in their two chief stages of de- 

 velopment, imago and larva, are therein analysed, 

 and by an examination of the respective forms it 

 has been attempted to discover the nature of the 

 causes which have led thereto. 



I may be permitted to say that the fact here 

 disclosed of a different morphological \ with the 

 same genealogical relationship, appears to me to 

 be of decided importance. The agreement of the 

 conclusions following therefrom with the results 

 of the former investigation has, at least in my own 

 mind, removed the last doubts as to the correct- 

 ness of the latter. 



The fourth and shortest essay on the " Trans- 

 formation of the Axolotl into Amblystoma," starts 

 primarily with the intention of showing that cases 

 of sudden transformation are no proof of per 

 saltum development. When this essay first ap- 

 peared the view was still widely entertained that 



