352 



VI. 



OBJECTIONS TO A PHYLETIC VITAL FORCE. 



IT has been shown in the previous section that the 

 three elements composing the markings of the 

 Sphinx-larvae originally possessed a distinct sig- 

 nificance with respect to the life of the species, and 

 that they were by this means called into existence. 

 It has likewise been shown, that in most of the 

 species which possess these characters at the pre- 

 sent time they still have a decided, although some- 

 times a different use, for their possessors, so that 

 from this point of view no objection can be raised 

 to their being considered as having arisen by 

 natural selection. 



On looking at the phenomenon as a whole, 

 however, certain instances occur which appear 

 quite irreconcilable with this view. 



The most formidable objection is offered by the 

 genus Deilephila. The row of ring-spots which 

 nearly all the existing species have more or less 

 developed, has arisen from a simple subdorsal line. 

 It would not, therefore, be surprising if a species 

 were discovered which possessed this line without 



