IS': 



THE EVOLUTION THEORY 



disposed to think, on this account, that the a.ucostovs ol' /). hi/ipopha't'f! 

 bore rings on all the .seii'nionts, and that these liad gradually lieeuiue 

 vestigial on the majority oi" them, hecanse tl\ey had lost their earlier 

 biological importance, and now, by adaptation to the buckthorn, could 

 only be of use on the second last. But when we take the ontogeny 

 also into account we find in the young caterpillar only a simple 

 sub-dorsal line, upon which, in the third stage, the red spot of the 

 tail-horn segment appears (Fig. S, A). 



No spots ever occur on the other segments at this stage ; they 

 only appear in the last stage, but as they may be entirely wanting, 

 they must have aiisen as the result of internal la\\s ol' correlation, 

 that is, they must be I'ecapitulations of the hindmost spots which 

 arose in the phylogcny through natural selection. We may conclude 



Fill. 1 18. Two st.iiyos ill the lifo-liisloiy ol'l ho Spurge Ilinvk-motli (Deiluphila 

 eiiplmiiiiif). A, lirst. stiigc, tlio catorpillnr d.'irk hlncUisli-sroon, without 

 inarking. B, second stiign, thn row of spots is clislinotly ooniUH'd'il li.\' a light 

 atroak, tho vosli^i< of thi> sub-dorsnl stript\ 



this, at least, if wi' believe in tlie truth of the fundamental proposition 

 of the biogenetic law, and admit that there is in the ontogeny soim^ 

 jinore or less distinct recapitulation ol' the phylogeny. 



This proposition maybe recognized as true in the case vi'i Dcilcpltila 

 also, if we compare the different species with one another as regards 

 their ontogeny. We find here too that not only the sub-dorsal, that 

 is, the phyletically oldest marking of tho JSphingid cMtei-])ilhvrs, occurs 

 everywhei'e in the young stages, but also that it is being slnnited 

 back to younger and younger stages, in proportion to tihe degrt-e of 

 the devH^lopmont ol' the spot-marking reached in the rnll-grown 

 caterpillar. Thus, for instance, in the caterpillar of l)cUt'i>liila 

 eu'pliorhhv. tlie highest form of spot-marking is reached, and in this 

 species the sub-doivsal line is no lougei' the sole marking element at 



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