380 Studies in the Theory of Descent. 



more perfect if they did not stand upon a white 

 line. 



If we consider the small number of facts with 

 which I have here been able to deal, the result 

 of these investigations will not be deemed unsatis- 

 factory. It has been possible to show that each 

 of the three chief elements of the markings of the 

 Sphingidce have a biological significance, and their 

 origin by means of natural selection has thus been 

 made to appear probable. It has further been 

 possible to show that the first rudiments of these 

 markings must also have been of use ; and it thus 

 appears to me that their origin by means of natural 

 selection has been proved to demonstration. 

 Moreover, it has not been difficult to understand 

 the displacement of the primary elements of the 

 markings by secondary characters added at a later 

 period, as likewise an essential effect of natural 

 selection. Finally, it has been possible to explain 

 also the subordinate or accessory elements of the 

 markings, partly by the action of natural selection, 

 and partly as the result of markings formerly 

 present acting by correlation. 



From the origin and gradual evolution of the 

 markings of the Sphingida we may accordingly 

 sketch the following picture : 



The oldest Sphinx-larvae were without markings ; 

 they were probably protected only by adaptive 

 colouring, and a large caudal horn, and by being 

 armed with short bristles. 



