the colours of certain Lepidoptera. 479 



The remaining black receptacles were always used in darkness, 

 sometimes with the addition of rugs and mats, sometimes without. 

 They were always placed open end downwards on a black tissue- 

 paper floor, except when the larvae were fed in them, and tliis was 

 only very occasionally. 



VIII. A cylinder similar to IV., covered with 2 layers of black 

 tissue-paper, and a roof of the same. 



IX. A smaller cylinder of tlie same kind, '71 decimetres 

 diameter, 1-53 high ; covered and roofed as iu VIII. 



X. A cylinder, probably of the same size as IX., or perhaps IV., 

 possibly domed like the succeeding ones. In any case, the cover- 

 ing was as in these. 



XI., XII., XIII., XIV. These 4 cylinders were "70 decimetres 

 diameter, 1-98 high, with the upper end domed, so that the diameter 

 was reduced to rather less than half that of the lower end. They 

 were all covered with 2 layers of black tissue-paper, and had roofs 

 of 2 or generally many more thicknesses. 



XV. A wooden box, about 3 decimetres long, 2 wide, and li 

 deep ; lined with black tissue-paper, and inverted on a floor of the 

 same. 



B. " Gilt " Surroundings. 



The various so-called gilt papers employed were in all 

 cases covered with " Dutch metal," a mixture of copper 

 and zinc, the proportion of the former metal being very 

 high. Three kinds of such gilt paper were employed : — 

 (1) The metal had been applied in the form of "leaf," 

 and bore a strong resemblance to true gold-leaf. The 

 surface was very bright and golden, but was not highly 

 polished. This was the only gilt-paper made use of in 

 my earlier experiments, and erroneously described as 

 "gold-leaf" in my paper (Phil. Trans., I.e., p. 324). It 

 will be spoken of as " Dutch leaf." (2) A very highly 

 polibhed metallic surface, often tending to become 

 tarnished and copper-like. This will be called "polished 

 Dutch metal." (8) A very similar metallic surface, 

 apparently not quite so brilliant, with an embossed 

 pattern on it. This will be called "embossed Dutch 

 metal." 



I wish to express my thanks to Mr. W. W. Fisher 

 and Mr. Walker for kindly analysing samples of these 

 and the " silver" papers employed, ni the Oxford Uni- 

 versity Laboratory. 



XVI. Alow wide cylinder, 2-38 decimetres diameter, 1-02 high; 

 lined with embossed Dutch metal, and a roof the same. The 

 external surface of cylinder and roof was covered with one layer of 

 black tissue-paper, and this receptacle was sometimes used for 



