The Origin of the Markings of Caterpillars. 389 



viz., in the red spots accompanying the oblique 

 stripes in several Smerinthus-\dxv&. Closer 

 analysis, however, enabled us to perceive most 

 distinctly the wide gulf that separates " analogous 

 variation " from the mystic phyletic vital force. 

 Nothing further remains therefore for the action 

 of this force in respect to the marking and colour- 

 ing of the Sphingida, since several even of the 

 subordinate markings can be traced to their 

 causes, only the " dorsal spots " of our two native 

 species of Charocampa having been referred to cor- 

 relation without decided proof. From the tem- 

 porary inability to explain satisfactorily such an 

 insignificant detail, no one will, however, infer 

 the existence of such a cumbrous power as a 

 phyletic vital force. 



The final result to which these investigations 

 have led us is therefore the following : The 

 action of a phyletic vital force cannot be recognized 

 in the marking and colouring of the Sphingidce ; 

 the origination and perfection of these characters 

 depend entirely on the known factors of natural 

 selection and correlation. 



