278 Studies in the Theory of Descent. 



independently of natural selection, may therefore 

 be considered as established, and indeed cannot be 

 disputed (Darwin's " correlation of growth''). In 

 the present case it appears to me that an innate 

 law of this kind, determining the backward trans- 

 ference of new characters, is deducible from the 

 instances already ^quoted in another sense, viz., 

 from the fact that in many cases characters which 

 are decidedly advantageous to the adult are trans- 

 ferred to the younger stages, where they are at most 

 of but indifferent value, and can certainly be of no 

 direct advantage. This is the case with the 

 oblique stripes of Smerint/ms, which, in the adult 

 larvae, resemble the leaf ribs, as will be shown 

 more fully later on, and, in conjunction with the 

 green coloration, cause these caterpillars to be very 

 difficult of detection on their food-plants. The 

 insects are easily overlooked, and can only be dis- 

 tinctly recognized on close inspection. 



Now these oblique stripes appear, in all the Sme- 

 rinthus caterpillars known to me, in the second, and 

 sometimes even in the first stage, i. e. in larvae of 

 from 07 to i centimeter in length. The stripes are 

 here much closer together than the ribs of any of 

 the leaves of either willow, poplar, or lime, and can 

 therefore have no resemblance to these leaves. 

 The young caterpillars are certainly not rendered 

 more conspicuous by the oblique stripes, since they 

 ean only be recognized on close inspection. It is 

 for this reason that the stripes have not been 

 eliminated by natural selection. 



