﻿156 THE ENTOMOLOGIST. 



I take it that the ground colour of a wing is the lowest in rank, 

 and primal, whilst bands and markings on it show more highly 

 evolved colours. If so, in Pieris and Colias, black is above white 

 and 3 T ellow ; but in Vanessa atalanta, below white and red; and 

 so on. This were certainly to assume that the rank of the 

 colours corresponds with their historical order of development. 

 It remains to be seen whether this be a legitimate assumption. 

 Moreover, as regarding the identity of ground and primal colour, 

 one must remember that a high colour may commence as a band, 

 and end by covering nearly the whole wing, in which case the 

 original ground colour would eventually appear secondary ; 

 hence arises a necessity for caution in making such assumptions. 



[In view of the experimental results afterwards obtained, I 

 may be permitted to point out that I had thus foretold before- 

 hand the priority of white to yellow (antithetically to Mr. 

 Cockerell's views) ; and of yellow to red, in order of development. 

 On the other hand, it will appear how utterly fallacious were all 

 my a priori speculations on the rank and behaviour of black ; and 

 also, I fear, on the relations of band and spot colours to ground 

 colour.] 



Now, as to progressive modifications, I prophesied by far the 

 most interesting and vitally important results from the use of 

 such reagents as the organic acids. For my reagents I divided 

 into two main classes: — 1st, those that are naturally present 

 in the insect itself, or in the plants that it feeds upon; and 2nd, 

 those altogether foreign to the insect and plant. In the first class 

 were included such reagents as formic, acetic, malic, citric, 

 succinic, oxalic, benzoic, and tartaric acids, &c. ; also, by an 

 extension, such oxidising reagents as potassic permanganate, 

 seeing that oxidation perhaps plays an important part in the 

 evolution of colours ; although an objection might of course lie 

 here against such reagents on account of possible chemical 

 action other than oxidation. In the second class I included all 

 such reagents as strong mineral acids (sulphuric, nitric, hydro- 

 chloric, &c.) ; strong alkalis, — ammonia, sodic hydrate, potassic 

 hydrate ; and any salts that might be tried, as, e.g., potassic 

 ferro- cyanide, potassic iodide, argentic nitrate, &c. Evidently 

 none of these could affect the insects in nature, — they are all 

 foreign reagents; therefore I considered that no progressive 

 modifications could be looked for from the use of these reagents, 

 but merely retrogressive ; for it seemed likely that by destroying 

 the present colourings they would reveal the earlier stages. 

 Subsequently, however, I noted that possibly these progressive 

 and retrogressive reagents were too sharply divided, since 

 "unnatural" reagents might produce the progressive modifica- 

 tions in experimenting, although in nature such modifications 

 have been brought about by other means. 



