TllK IMOGKNHTIC 1,A\V 18S 



!\iiy s(;ioo. l-oaxino' oiil of tlio (pu'stion tlic absohiti'ly uninjirked 

 littlo oatorjnllar which o)uorj>v« from tho oi;->;- (Fig. i:iN, A), tlioro 

 aj^poars at oiu'o in tho sooond staye a sorios of riiii;--spots connoetod 

 by a ti)io whito siih-doi-sal hno (Fij;". 1 1 S, ./>'). In the followinLj 

 sta<;v, the thinl, tins s\ih-dorsal lino disaj^poars witliout loa\ ini;- 

 a trai'o, and theiv remains only the spot-markinif, which is svihse- 

 tpiontly dnplicatod. 



Let ns compare with (]\is the ontogeny of tho hod-straw liawk- 

 \\\ot\\,J\>ih>pliila ;/((/// (Fi>>'. 1 17). Tho fnll-yrown caterpillar possesses 

 only a siuolo nwv of rinj^-spots (/>), and accordiuijly the youno- 

 stages of tho cater}>illar up to the fonrth slunv a distinct suh- 

 doi-sal lino (.1), although spots are seen \ipon it. A still oarlior 

 phylotic stnge of development is illustrated by Ih'ilcphila lironuca, 

 in which tho ring-spots are all connoetod by tho snb-doi-sal lino. 



It C!in thus hardly bo doubted th;it the biooonetic law is guiding 

 ns aright when we conchule from a comparison of tho ontogeny of 

 (ho ditlorent species of DriJi'phihu that the oldest ancestors of the 

 genus possessed only tho longitudinal stripes, and that fivm those 

 small pieces wore cut ott as ring-spots, and that those wore gradually 

 perfected and ultimately ilu}^lica(ed, while at the .same time the 

 original marking, tho longitudinal stripe, was shunted hack further 

 and further in the young stages, until it tinally disappeared 

 altogotlior. 



Ijii us niiw rofo)- for a u\omont to tho thin! forn\ of marking 

 in tho caterpillars of tho Sphingida^ — transvoi-so striping, 'i^hisjiiis 

 not arisen out of the sub-dorsal line^ but quite independently and at 

 a later date. This is proved with great certainty by the ontogeny 

 of species of tho genus S)i,,n»thii^. Tho full-grown, and usually also 

 (ho young caterpillars, of these .species have quiti^ regularly the seven 

 bnvid ol^liquo stripes which run in the direction of tho tail-horn 

 at oipial intervals on tho lateral surfaces of the body (Fig. ■^). 

 They are absent only ftxnn tho tl\roe anliM-ior segments, and upon 

 those a part of (ho older marking, tho snb-dors,al stripe, hajs persisted. 

 Hut wo lind this fully developed in the youngest stages of other 

 spix'ios. In Sii)erii)ihiti< popufi, the little caterpillar, which has no 

 markings at all when it leaves the egg. very .soon .shows tho white 

 suh-dorsjvl lino, and siutultanoously with it the seven transverse 

 stripes, which cut obliquely through it; in tho older caterpillars tho 

 sulvdors;>l then di.sappears (Fig, 1.19). 



When 1 was ii\ves(ig:\ting these matters at tho beginning of the 

 sovontios 1 did i\ot sueoood in procuring ogg"s of the species of tho 

 genus S/J»in,>\ which likewise almost all exhibit the oblique striping 



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