xii Translator s Preface. 



to rise as a whole, cases may occasionally occur 

 where a lower grade of organization is better 

 adapted to certain conditions of life. This 

 principle of <( degeneration " was recognized by 

 Darwin as early as in the first edition of the 

 " Origin of Species ;" it was soon perceived to be 

 applicable to the phenomenon of parasitism, and 

 was first definitely formulated by Dr. Anton 

 Dohrn in 1875. In a lecture delivered before the 

 British Association at Sheffield in 1879, Prof. 

 E. Ray Lankester ascribed to " degeneration " a 

 distinct and well-defined function in the theory of 

 descent. Dr. Weismann's explanation of the 

 transformation of Axolotl given in the fourth 

 essay of this work, may be regarded as a special 

 contribution! to this phase of Darwinism. Whilst 

 refuting the idea held by certain naturalists, that 

 such cases are arguments against the origin of 

 species by the accumulation of minute variations, 

 and prove the possibility of development per 

 saltum, the theory here advanced (that Siredon 

 at a former period existed at a higher stage of 

 development as Amblystoma, and that the observed 

 cases of metamorphosis are but reversions to this 

 lost higher stage) suggests the question whether 

 there may not still be in existence many other 

 degenerated forms quite unsuspected by natural- 

 ists. 



Many of the opponents of Evolution have from 

 time to time denounced this doctrine as leading 



