^■^ ^I^D ^""^f^ 



JOURNAL OF VARIATION. 



No. 11. Vol. I. February 16th, 1891. 



MELANISM AND MELANOCHROISM IN BRITISH 

 LEPIDOPTERA. 



By J. W. TUTT, F.E.S. 

 {Contiimed fvoni page 234.) 



EFORE leaving altogether the general question of an 

 exciting cause, there are one or two points which we 

 should not overlook in our inferences and experiments. 

 The first is the influence of " heredity." Throughout 

 my paper I have assumed that my readers would always take this 

 comparatively and undoubtedly inconstant (in different species) 

 factor into account. But, it appears advisable to mention the 

 fact here, because, in certain experiments, its influence might be 

 so potent, that it would be really the most powerful factor actmg 

 at the time, and yet its influence might be altogether over- 

 looked. Under the artificial conditions of domestication, we 

 know this power is a very great and important one, and there 

 is no doubt, that what is applicable to the artificial conditions 

 of life in the higher animals, must influence, more or less, 

 insects kept under similar artificial conditions. Where insects 

 have a normal tendency to vary, and where artificial breeding 

 gives all sorts of strange varieties under apparently the same 

 or similar conditions, it is manifestly impossible to conduct 

 exact experiments with a species having the influence of 

 heredity strongly developed, with any probability of arriving 

 at a satisfactory result. I have, for example, in my collection, 

 specimens of Selenia illiistraria, which might belong to either 

 the spring or summer brood, so far as colour is concerned, and 

 which would puzzle me entirely if I did not know to which brood 

 they really did belong. Captured specimens of this species 



