210 SEXUAL DIMORPHISM 



white with colourless margins. In the adult the brown 

 bands are bright yellow, the white bands blue with gray 

 margins. The brown bands in the young are found, on 

 microscopic examination, to derive their colour from numerous 

 yellow and black chromatophores, lying immediately beneath 

 the epidermis, which is colourless. Besides definite black 

 chromatophores there is a network of strands of granular 

 matter, brown by transmitted light, pale yellow by reflected 

 light, and evidently of the same nature as the pigment of 

 the black chromatophores. Mr. Holt describes aggregations 

 of this brownish substance as degenerate chromatophores, 

 from which I infer that the reticular strands contain melanin 

 in very thin lines, the lighter coloration being merely due to 

 the smaller quantity of the pigment present at any one spot. 

 The general brown colour of the bands is, therefore, due to a 

 mingling of brown and yellow dots. In the adult male 

 these brown bands become bright yellow in consequence of 

 the reduction in number or entire loss of the black chromato- 

 phores, and the excessive' development of the yellow pigment. 

 The latter appears diffuse and continuous, until some of it is 

 removed from a piece of skin by a reagent, and then separate 

 yellow stellate chromatophores are visible. The black 

 chromatophores present in the younger stage are represented 

 by a complete network of granular matter, the colour of 

 which is too feeble to affect that of the abundant yellow 

 pigment. 



The white bands in the young contain a few black 

 chromatophores, but their whiteness is due to a granular 

 reflecting matter, arranged in an irregular network. In the 

 adult the white bands become blue, and in them are a few 

 contracted black chromatophores. The brilliant blue colour 

 is due to a dense network of bundles of small bean-shapecl 

 bodies. These are yellow by transmitted light, but intensely 

 blue by reflected light over a black background, such as that 



