286 THE ENTOMOLOGIST. 



If only certain species of the genus Vanessa had been used for 

 analysing this problem, it would have been on a casual examina- 

 tion a tempting speculation to suppose, taking as a basis certain 

 highly darkened aberrative forms resembling each other, that 

 aberrations were retrogressions in the direction of an ancient 

 type, having characteristics common to these species. There are, 

 however, such important reasons against the acceptance of this 

 view that it certainly cannot be correct. One of these reasons 

 is that in these aberrations the males are not only much more 

 numerous than the females, but are also inclined to the most 

 extreme development ; whereas we know by experience that the 

 female sex is far more inclined to atavism. 



The most important reasons which preclude the possibility 

 of the variations being atavistic are grounded on phylogenetic 

 considerations. In considering the genus Vanessa and the re- 

 lated nymphalids Argynnis and Melitcea, we must reach the con- 

 clusion that this is not a case of primarily black or dark-coloured 

 ground colour and secondary light brown and yellow, which 

 would be the result if we were to consider these darkened aber- 

 rations as atavisms, but, on the contrary, primarily yellow or 

 light brown ground colours with secondary superposition of 

 darker markings. We have right amongst palsearctic Vanessidse 

 two species which show the phylogenetic progress from light 

 brown ground colours with dark markings to a predominating 

 dark brown ground colour in a seasonal dimorphic form, viz. V. 

 levana, L., and the related Siberian V. burejana, Brem. 



If, however, the aberrations cannot be considered as forms 

 tending in an atavistic direction, what are they ? 



Eegarding the influence of the experiment, they cannot be 

 considered as the direct result of this influence, but solely as a 

 frequent but by no means constant accompaniment. The direct 

 result of the experiments is lethargy, interruption of the develop- 

 ment, at a stage of life-history when important changes in the 

 structure of the body have naturally a fundamental influence on 

 the colour garb of the imago. These interruptions destroy the 

 continuity of the normal development, which holds, so to speak, 

 the individual fettered, driving it forward in a certain direction ; 

 when the further development continues, a portion of the indivi- 

 duals — in fact, the majority — continue in the usual direction ; a 

 few, however, diverge from the normal direction of development, 

 as if thrown off the rails by the interruption. 



It is therefore a case of a relatively independent progressive 

 development of the individual, and therefore with a stamp of 

 great variation between individuals. The aberrations therefore 

 indicate, firstly, individual colour anomalies in a new direction 

 (at least in most cases). 



But still another side of their character presents itself : if we 



