The Origin of the Markings of Caterpillars. 285 



III. 



BIOLOGICAL VALUE OF MARKING IN GENERAL. 



HAVING now described the development of larval 

 markings, so far as possible from their external 

 phenomena, and having traced therefrom the 

 underlying law of development, I may next pro- 

 ceed to the main problem the attempt to discover 

 those deeper inciting causes which have produced 

 marking in general. 



The same two contingencies here present 

 themselves as those which relate to organic life as 

 a whole ; either the remarkably complex and ap- 

 parently incomprehensible characters to which we 

 give the name of markings owe their origin to 

 the direct and indirect gradual action of the chang- 

 ing conditions of life, or else they arise from 

 causes entirely innate in the organism itself, i. e. 

 from a phyletic vital force. I have already stated 

 in the Introduction why the markings of cater- 

 pillars appear to me such particularly favourable 

 characters for deciding this question, or, more 

 precisely, why these characters, above any others, 

 appear to me to render such decision more easily 



