142 M. I. NE WBIGIN [fee. 1899 



the origin of both, and the relation between the development 

 of dark pigments and of optical colours. When these points 

 have been determined, we may hope to be able to take a fresh 

 survey of the whole field of colour, with some prospect of reaching 

 definite conclusions as to the immediate cause of colour variation. 

 The colour variations of the Lepidoptera have always been objects 

 of great interest, and it may be looked upon as a hopeful sign 

 that so many biologists are endeavouring to discover their evolution 

 value, instead of being content to point out how they may be useful 

 to the species. 



Finally, whatever may seem doubtful or speculative in Piepers' 

 suo-oestions, his observations, together with those of the other authors 

 named, point at least to one definite conclusion which is worth 

 emphasis. They seem to confirm the view, supported by many recent 

 investigators, that there is an intimate connection between the colours 

 of organs and their general structural peculiarities. Thus, in the 

 present case the colours of individual scales do not change very 

 markedly in development, but the early scales with their primitive 

 tints are covered up by scales bearing the hues of the imago. Similarly, 

 in the adult, scales exhibiting the more primitive colours are of simple 

 structure, and are replaced in phylogeny by scales of more complex 

 structure and more specialised tint. This is a point of much import- 

 ance, for it tends to show how far colour changes are from being- 

 superficial, how intimately they are connected with the other char- 

 acteristics of the organism. 



REFERENCES 



1. Baer, M., "Ueber Bau und Farben der Fliigelschuppen bei Tagfaltern," Zcitschr. f. 



wiss. Zool., 1898, lxv. pp. 50-64. 



2. Hopkins, F. Gowland, "The Pigments of the Pieridae," Phil. Trans. Roy. Soc, 



1S96, clxxxvi. pp. 661-682. 



3. Linden, Maria von, " Untersuchungen iiber die Entwickelung der Zeichnung des 



Schmetterlingsfliigels in der Puppe," Zcitschr. f. tviss. Zool., 189S, lxv. pp. 1-49, 

 3 pis. 



4. Newbigin, M. I., "The Pigments of Animals," Nat. Sri., 1896, viii. pp. 94-100 



and 173-177. Sec also "Colour in Nature," London, 1898. 



5. Piepeus, M. C, "Die Farbenevolution (Phylogenie der Farben) bei den Pieriden," 



Tijdschr. Nederland. Dicrkund. Vcr., 1898, v. pp. 70-289. 



School of Medicine for Women, 

 Edinburgh. 



