The Origin of the Markings of Caterpillars. 1 89 



portions of it, the eye- spots of the fourth and fifth 

 segments became developed. After the per- 

 fecting of the eye-spots, weak repetitions of the 

 latter appeared as black spots on all the segments 

 except the last. 



In Porcellus the caterpillar emerges from the 

 egg with the subdorsal line, the first stage of 

 Elpenor being omitted, From this fact we may 

 venture to conclude that Porcellus is the younger 

 species, or, what comes to the same thing, that 

 it has further advanced in development. The 

 whole subsequent history of Porcellus agrees with 

 this view, its course of development being essen- 

 tially but a repetition of the phenomena displayed 

 by Elpenor, and differing only in one point, viz. 

 that all new characters make their appearance 

 one stage earlier than in the latter species. This 

 is the case with the transformation of the green 

 into a brown ground-colour ; with the repetition of 

 the eye-spots on the remaining segments in the 

 form of suffused black spots ; and with the appear- 

 ance of the light " dorsal spots." Only the eye- 

 spots themselves appear, and the snout-like taper- 

 ing of the front segments occurs in the same stage 

 as in Elpenor ; i. e. the second. 



From these data alone, we may venture to infer 

 the occurrence of four chief stages in the phyletic 

 development of the genus. The first stage was 

 simply green, without any marking ; the second 

 showed a subdorsal line ; the third, eye-spots on 



