The Origin of the Markings of Caterpillars. 325 



selection, but by a hypothetical phyletic force. 

 We should then expect to see them appear at some 

 period in the course of the phyletic develop- 

 ment perhaps at first only in solitary individuals, 

 then in several, and finally in all ; but we certainly 

 could not expect that at first single, irregular, 

 coloured spots should arise in the neighbourhood of 

 the oblique white stripes that these spots should 

 then multiply, and fusing together, should adhere 

 to the white stripes, so as to form an irregular 

 spot-like edge, which finally becomes formed into 

 a straight, uniformly broad stripe. The phyletic 

 development of the coloured edges takes place, 

 however, in such a manner, the species of Smerin- 

 thus, as has already been established, showing 

 this with particular distinctness. In S. Tilice the 

 course of development can be followed till the 

 somewhat irregular red border is formed. In the 

 species of Sphinx this border has become com- 

 pletely linear. It is very possible that the ontogeny 

 of 6*. Ligustri or Drupiferarum would reveal the 

 whole process, although it may also be possible 

 that owing to the contraction of the development, 

 much of the phylogeny is already lost. 



I have now arrived at the consideration of the 

 last kind of marking which occurs in the Sphin- 

 gid(z> viz. : 



4. Eye-spots and Ring-spots. These markings, 

 besides among the Sphingidce, are found only in a 

 very few caterpillars, such as certain tropical 



