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 larve 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 held 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. 
