﻿312 THE ENTOMOLOGIST. 



just such a cosmopolitan colour as this seemed black (as also 

 white) ;* great was the interest with which I commenced working 

 at it ; and commensurately great my disappointment at the total 

 failure. However different the reactions of its associated colours, 

 black is always the same and unaffected — " Quod semper, quod 

 ubique, quod ab omnibus." It is incredible to me that if black 

 were a pigment colour it should be impervious to all my reagents 

 —with whatever other pigment colours it be associated. I cannot 

 believe that, in all the species just enumerated, pigments of half-a- 

 dozen different colours should have been evolved, and in associa- 

 tion with each a black pigment (which must be genetically somehow 

 related to its companion, both being produced by the metabolic 

 activities of the same system), always the same and always 

 immovable. I conclude therefore, with considerable confidence, 

 that black is no pigment colour, but a mere physical absorption 

 result. Conformable with this is the fact that in the dozen or so 

 instances where the black was a trifle affected, no colour was 

 produced, but merely a less black black, — a faded, washed out, 

 brownish black: and this is just what one might expect (ifblackbea 

 physical colour) as the result of my reagent that partially destroyed 

 the structure of the scales.t Black, then, I regard as being due 

 — in Lepidoptera — to an arrangement of scales such as to cause 

 a total absorption of all the incident light rays.+ This absence 

 of any black pigment is the more astonishing in face of its 

 common occurrence in other orders of the animal kingdom. It 

 would seem pretty clear that in most animals (i. e. Mammalia), in 

 the normal animal as distinguished from the albino, there is a 

 black pigment in the regions of the mouth, eyes, &c.,§ and in the 

 Negro there is a distribution of presumably black pigment over 

 the whole skin surface. I am not aware how far down in the 

 scale black pigments have been definitely found : possibly 1 — it is 



* In connection with this it should be pointed out that in my anticipatory 

 theoretical reflections, before any experimental data were to hand, I had conjectured 

 that several different blacks might exist, — so protean are its combinations. See 

 Entom. p. 156. 



t One final explanation conld be hazarded. It has been suggested to me, by a 

 friend, that in some species the colours may be enclosed in chitinous, transparent 

 cases, — microscopic quills as it were, — and be thus rendered impervious to re- 

 agents. I am not, however, aware that this is anything more than a conjecture, 

 and nothing in the appearance of the wings, when examined microscopically, 

 suggests this to me. But anyhow it seems to me an utterly impossible proposition 

 that black pigment is always enclosed in such chitinous receptacles, although com- 

 bined with every other colour susceptible to chemical reagents, and therefore — pre- 

 sumably — not chitinously protected. I think we may with perfect safety ignore any 

 such explanation as this of black's behaviour. 



| But at the same time I am quite open to the reply that this theory, that black 

 is no pigment colour, is only at best a probable assumption, and not strictly demon- 

 strated. That is quite true ; but I think it a very probable assumption, and at any 

 rate we must accept it for the present as a working hypothesis. 



§ Vide the interesting statements made by Wallace in ' Tropical Nature.' 

 I should say, however, that Wallace does not explicitly state it to be a black 

 pigment, though his expressions imply that. He merely says a " dark pigment." 



