70 THE STRUCTURE OF MAN 
Fic. 50.—AN ATTEMPT TO DEPICT DIAGRAMMATICALLY THE PROCESS BY WHICH, FROM 
THE STUDY OF COMPARATIVE MORPHOLOGY, THE LIMBS OF TERRESTRIAL VERTE- 
BRATA WOULD APPEAR TO HAVE BEEN PROBABLY DERIVED, BY MODIFICATION, 
FROM THE FINS OF FISHES. 
The shaded parts indicate rays which atrophy; A, pelvic fin of a Sturgeon; B, 
diagram of the posterior limb of a larval Salamander; C, the hind limb of 
an adult Urodele Amphibian (Ranodon) ; p., pelvis; bs., basale (femur); rd’., 
proximal rays (tibia, fibula); r.y., peripheral ray segments (tarsal and other 
elements of the pedal skeleton); rd’’., rays which atrophy and ultimately 
disappear. 
