SCIENTIFIC NOTES AND OBSERVATIONS. 39 



put down as this for a long time now ; I may say, ever since Darwin 

 first commenced to work at secondary sexual characters ; but althougl) 

 I grant this in both m}' papers, " The genetic sequence in insect 

 colours " (Brit. Noct., vol. ii.) and Secondary Sexual Characters (Brit. 

 Noct., vol. iii.), I have, as is well known, not accepted wholly (nor 

 even largel}' in part) Darwin's conclusions thereon. In fact, I have 

 preferred Wallace's explanation (with some slight modifications), in 

 preference to that of Darwin. With regard to Dr. Freer's note on Thechi 

 rnbi, is he sure that this green is one of the "potential " colours. I have had 

 a suspicion lately that, like Lf/cania adonis, L. corydon, I'rocris statices, 

 and a few other species which change colour in the presence of water 

 vapour, that the scales themselves may hold tlie vapours externally, and 

 thus alter their reflective power, and influence the ordinary diffraction. 

 Try any of these species in a damp box for a short time, and what I 

 mean will, I think, be clear ; but it may be a " potential " colour, and 

 then, the rapid change, even when absorbing the water-vapour, is re- 

 markable. So far as the phylogenetic significance of chemical reaction 

 goes, it appears to amount to this : — Certain species have natural va- 

 rieties; the influence of certain chemical reagents produces these 

 varieties ; enjo, the pigmental change brought about in natural varieties 

 can be brought about by chemical reagents. Other species, not given 

 maybe to variation, similarly under chemical reagents, give certain de- 

 finite changes ; the generic relations often show that this change is the 

 normal colour of allied species. Certain allied species give under 

 chemical reagents a common result ; surely such of these as have been 

 definitely worked out, tend strongly to suggest that they may have a 

 real phylogenetic significance. If not, why not ? Dr. Freer's notes 

 re " white " and " green " as derivatives of yellow, are not altogether 

 clear. If ammonia turns some whites "yellow," is it not clear that 

 there is in the white some substance — pigment-factor — in the insect 

 which has probably been converted into its present form from yellow, and 

 which is being changed back, as it were, by the reagent ; or, on the 

 other hand, that there is some substance in the insect's scales, that under 

 some slight natural change may develop yellow, and if we accept either 

 of these alternatives with regard to green, does not the fact that the 

 white and the green both have a yellow base, show that they are con- 

 nected through the yellow ? I ask this in all innocence. It seems to 

 me the only logical position to take up. Nor do I understand lohy 

 nothing can be deduced concerning the behaviour of " chemicals 

 towards the colours of insects, until the colour (? pigment, J. W. T.) 

 has been dissolved out and isolated." Nature works on the pigments 

 as they are, and does not dissolve them out, nor isolate them to do so. 

 Does Dr. Freer assert that no insect's colours are pigmentary ? If so, 

 what becomes of his " pigment granules," which are seen so abundantly 

 under the microscope ? Are these pigment granules then to be con- 

 sidered the normal expression of physical colours due to interference 

 and diffractitm ? If not, why must we consider all colours " potential, 

 physical, or what we will, but not pigmentary?" What again does 

 Dr. Freer refer to, when he talks of colours whose "sole claim rests on 

 their naked eye appearance?" I remember my friend Mr. Coverdale 

 dissolving out the red pigment-factor in Vnnetisa to, but I cannot lay 

 my hand on the note with the details. What Dr. Freer says is quite 

 true about the possibility of the scale structure, but it does not alter the 



