PHYSIOGENESIS. 237 



sheet, the boss of silk was carefully scraped off and 

 was pinned on the upper color, above one of the holes, 

 so that the head and first five body-rings passed 

 through the hole on to the color beneath, which tended 

 to produce opposite effects. Other larvae were simi- 

 larly fixed between the shelves upon one color only, so 

 as to afford a comparison with the results of the con- 

 flicting colors. 



"A careful comparison of all the pupae obtained in 

 the conflicting color experiments showed that, when 

 the illumination of the two surfaces was equal, the ef- 

 fective results were produced by that color to which 

 the larger area of skin had been exposed, whether the 

 head formed part of that area or not. Particolored 

 pupae were never obtained. It therefore appears to be 

 certain that the skin of the larva is influenced by sur- 

 rounding colors during the sensitive period, and it is 

 also probable that the effects are wrought through the 

 medium of the nervous system. The latter conclu- 

 sion receives further confirmation from other observa- 

 tions." 



Professor Poulton has since produced remarkable 

 color-changes in the larvae of Lepidoptera by confin- 

 ing them to the branches of plants of distinct colors. 

 Thus geometrid larvae confined to the stems of a black 

 color, became correspondingly dark ; while those re- 

 stricted to white twigs became very pale. These larvae, 

 and, still more strikingly, those of Cossus lignipcrda, 

 when confined on branches which supported lichens, 

 became of variegated colors, corresponding with those 

 of the lichens, and affording an admirable means of 

 concealment. 



