3QO Studies in the Theory of Descent. 



n. 



ON PHYLETIC PARALLELISM IN METAMORPHIC 

 SPECIES. 



INTRODUCTION. 



IN the previous essay I attempted to trace a 

 whole group of apparently " purely morpho- 

 logical " characters to the action of known factors 

 of transformation, to explain them completely by 

 these factors, and in this manner I endeavoured 

 to exclude the operation of an internal power 

 inciting change (phyletic vital force). 



In this second study I have attempted to solve 

 the problem as to whether such an innate inciting 

 power can be shown to exist by comparing the 

 forms of the two chief stages of metamorphic 

 species, or whether such a force can be dispensed 

 with. 



Nobody has as yet apparently entertained the 

 idea of testing this question by those species which 

 appear in the two forms of larva and imago 

 (insects), or, expressed in more general terms, by 

 those species the individuals of which successively 

 possess quite different forms (metamorphosis), or 



