﻿340 THE ENTOMOLOGIST. 



in interpreting these experiments, it must not be said that yellow 

 has been evolved from white, in the same sense as red has been 

 evolved from j'ellow : this conception would be quite erroneous. 

 Yellow, although evolved on or in a white wing, has not been 

 evolved from white ; that is to say, it has nc genetic connection 

 with white, as, for instance, red has with yellow. It is a neces- 

 sary corollary, from this statement, that the so very usual con- 

 nection of j^ellow and white (in the sense that probably most 

 yellow species were formerly white) is, chemically considered, a 

 mere accident or coincidence, and that there is no reason why 

 yellow might not equally well have been developed on any other 

 unpigmented* ground colour, as, for example, on a black, or grey, 

 or brown.f Now the chestnut-coloured pigment, as I have strong 

 reason to believe, is pretty closely related chemically to yellow, 

 and is entirely analogous to yellow in that it also, though deve- 

 loped so commonly on originally white species (as is shown by 

 the fact that reagents dissolve it out, and leave a white wing), 

 has also no genetic relationship to white — no necessary connection 

 therewith. In this connection, therefore, I consider it exceedingly 

 interesting that the reactions with two chestnut species that offer 

 apparently striking exceptions to the behaviour of the class gene- 

 rally, are really — according to the view just enunciated — quite 

 normal ; and in fact it is in the behaviour of these very species 

 that we find a striking confirmation of this theory of the relations 

 between chestnut and white, and therefore indirectly, and by 

 analogy, of my theory concerning yellow also. But I must not 

 further anticipate results that will be fully explained under sub- 

 sequent headings. 



With regard now to the absence of any white .pigment, I 

 do not think that we have here by any means so mucE cause 

 for surprise as in the corresponding case of black ; at least, 

 so it seems to me now, looking at the matter in the light of 

 past experience ; but I am disappointed that my experiments 

 should prove of no value in differentiating the various whites into 

 different groups, and especially am I disappointed in the results 

 of the special set of staining experiments.! After considering 

 these carefully I cannot perceive that there are any particular 

 inferences to be drawn, except that the whites of Pieris and 

 Melanargia are somewhat different from the others — which we 

 knew before. Now it had appeared to me (reasoning from the 

 mere appearance of the different whites) that one might divide 

 them into several groups, as, for instance : — 1. Pieris ; 2. Mela- 

 nargia ; 3. Vanessa, Limenitis, and perhaps the Noctuce with white 

 hind wings ; 4. Hepialus ; 5. Liparidse ; and so on. Such an 

 attempt at arrangement by superficial resemblance would, how- 



* The reason for this restriction of " wmpigmented " is of course obvious, 

 t Further consideration of this is deferred until Section 6. 

 I See page 220. 



