Phyktic Parallelism in M dimorphic Species. 431 



called " complete " metamorphosis of insects 

 n ? the answer can only be : through the 

 gradual adaptation of the different stages of 

 development to conditions of life which have con- 

 tinually deviated more and more widely from each 

 other. 4 



But if individual stages of the post-embryonic 

 development can finally attain to such complete 

 diversity of structure as that of the larva and imago 

 through gradual adaptations to continually diverg- 

 ing conditions of life, this shows that the charac- 

 ters acquired by the single stages are always only 

 transferred to the same stages of the following 

 generation, whilst the other stages remain unin- 

 fluenced 'thereby. This depends upon that form 

 of heredity designated by Darwin " inheritance 

 at corresponding periods of life," and by Haeckel 

 " homochronic heredity." 



* In this sense Lubbock says : " It is evident that creatures 

 which, like the majority of insects, live during the successive 

 periods of their existence in very different circumstances, may 

 undergo considerable changes in their larval organization in 

 consequence of forces acting on them while in that condition ; 

 not, indeed, without affecting, but certainly without affecting to 

 any corresponding extent, their ultimate form." " Origin and 

 Metamorphoses of Insects," London, 1874, p. 39. 



