348 Studies in the Theory of Descent. 



base of their food-plants among the dead leaves 

 and branches. I do not consider this reticulation 

 to be a distinct imitation, but only as one of the 

 various means of breaking up the large uniform 

 surface of the caterpillar so as to make it present 

 inequalities, and thus render it less conspicuous. 

 There can be no doubt as to the dependence of 

 this character upon natural selection. 



There is, however, a second group of markings, 

 which must be referred to another origin. To 

 this group, for instance, belong those light dots 

 in Cheer ocampa Porcellus and Elpenor which have 

 been termed " dorsal spots." I know of no other 

 explanation for these than that they are the neces- 

 sary results of other new formations, and depend 

 on correlation (Darwin), or, as I may express it, 

 they are the result of the action of the law govern- 

 ing the organization of these species. 



As long as we are confined to the mere sup- 

 position that the character in question may be 

 the outward expression of an innate law of growth, 

 it is permissible to attempt to show that a quite 

 similar formation in another species depends upon 

 such a law. 



Many of the dark specimens of Sphinx Convol- 

 vuli show whitish dots on segments six to eleven, 

 one being situated on the front edge of each of 

 these segments, at the height of the completely 

 vanished subdorsal line (Fig. 52). These spots 

 vary much in size, lightness, and sharpness of 



