1 98 Studies in the Theory of Descent. 



species of the third group the ocelli on the hind 

 segments have a secondary origin through a 

 repetition of the primary ones of the front 

 segments, but we can also establish that the same 

 species in two different regions may arrive at two 

 different phyletic stages. 



If, finally, we sum up the facts taught by the 

 ontogeny of the two German species, and the 

 adult forms of the other species, we can form 

 therefrom a tolerably complete picture of the 

 course of development of the genus Chczrocampa. 

 Of the four phyletic stages indicated by the 

 ontogeny of Elpenor and Porcellus, three still 

 form the terminus of the development of exist- 

 ing species. The great differences among the 

 caterpillars of this genus can be very simply ex- 

 plained on the view that they stand at different 

 levels of phyletic development ; some species 

 having remained far behind (Group i), others 

 having advanced further (Group 2), and others 

 having reached the highest point of development 

 (Group 3). The fact that the species of the third 

 group are only tropical accords well with this view, 

 since many facts prove that phyletic development 

 proceeds more rapidly in the tropics than in 

 temperate climates. 



The striking markings of the Ch&rocampa 

 larvae may, in brief, be stated to originate from a 

 local transformation of two portions of the sub- 

 dorsal line into eye-spots, and the subsequent 



