▁theory ▁of ▁evolution . ▁ ▁As ▁a ▁professor ▁of ▁an atom y ▁at ▁the ▁University ▁of ▁J ena ▁( 1 8 5 5 – 1 8 7 3 ) ▁and ▁at ▁the ▁University ▁of ▁Heidel berg ▁( 1 8 7 3 – 1 9 0 3 ), ▁Karl ▁Gegen ba ur ▁was ▁a ▁strong ▁supp orter ▁of ▁Charles ▁Dar win ' s ▁theory ▁of ▁organ ic ▁evolution , ▁having ▁taught ▁and ▁worked , ▁beginning ▁in ▁ 1 8 5 8 , ▁with ▁Ernst ▁H ae ck el , ▁ 8 ▁years ▁his ▁junior . ▁ ▁Gegen ba ur ' s ▁book ▁Grund z üge ▁der ▁ver gleich enden ▁An atom ie ▁( 1 8 5 9 ; ▁English ▁translation ▁Element s ▁of ▁Compar ative ▁An atom y ▁by ▁Francis ▁Jeff rey ▁Bell , ▁ 1 8 7 8 ) ▁became ▁the ▁standard ▁text book , ▁at ▁the ▁time , ▁of ▁evolution ary ▁morph ology , ▁emphas izing ▁that ▁struct ural ▁similar ities ▁among ▁various ▁animals ▁provide ▁cl ues ▁to ▁their ▁evolution ary ▁history . ▁Karl ▁Gegen ba ur ▁noted ▁that ▁the ▁most ▁reliable ▁clue ▁to ▁evolution ary ▁history ▁is ▁hom ology , ▁the ▁comparison ▁of ▁an atom ical ▁parts ▁which ▁have ▁a ▁common ▁evolution ary ▁origin . ▁ ▁Gegen ba ur ▁had ▁been ▁a ▁student ▁of ▁Albert ▁von ▁K öl li ker , ▁Rudolf ▁Vir ch ow , ▁Heinrich ▁Müller ▁and ▁Franz ▁Le yd ig ▁( 1 8 2 1 – 1 9 0 8 ). ▁ ▁Life ▁Karl ▁Gegen ba ur ▁was