FIG. 20. Development of the hind foot of a 

 salamander, Triton tceniatus. After Strasser, 

 from Lull's "Organic Evolution," published 

 by the Macmillan Company. 



FIG. 21. Foot of a reptile, Ranodon 

 sibericus: f, fibula; h, femur; /, 

 tibia; I, II, III, IV., digits 1-5. 

 After Wiedersheim, from Lull's 

 "Organic Evolution," published by 

 the Macmillan Company. 



