418 Mr. E. B. Poulton. Experimental Proof that the Colours 



no chlorophyll, while the food of the second contained only a little 

 etiolin, and that so situated (around the fibrovascular bundles and 

 buried deeply in the substance of the mid-ribs) that the larvae could 

 not make use of it, while the food of the third contained abundant 

 chlorophyll. 



It is evident that any constant difference between the larval colours 

 in the three sets followed from these differences in the food supplied 

 them ; and, unless there are reasons for believing that the differences 

 were due to pathological change, and thus an indirect result of the 

 food, we must hold that they are a direct result, and that important 

 elements of the larval colouring are dependent on the existence of some 

 modification of pigments derived from their food. 



The course of the experiment will now be described in a tabular 

 form. 



