242 



COMPARATIVE ANATOMY 



/m///y. 



Fig. 200. — Diagrams illustrating theories of origin of appendages. A, B, C, origin 

 of biserial appendage (C) from gill arch {A)\ D, biserial appendage (archipterygium) ; 

 E, F, evolution of elasmobranch fin; G, dotted lines indicate parts involved in origin of 

 leg from fin; H, dotted parts show another view of origin of elements of leg. (From 

 Kingsley's "Comparative Anatomy of Vertebrates.") 



PHALANGES 



METACARPALS 



BCHElROPTERYGIUM, 



Fig. 20I. — Diagrams of the pectoral appendages of lower and higher vertebrates. 

 A persistent problem of morphology is how the fish extremity or ichthyopterygium was 

 transformed into the fingered extremity (cheiropterygium) of land vertebrates. 



