VI. 



THE COMMON FROG. 



we find a structure very similar in form in animals 

 remote enough from Batrachians, yet rarely do we 

 find such in any intermediate kinds. Thus in certain 

 tree-porcupines the ankle is furnished in like manner 

 — another instance of the independent origin of 

 strikingly similar structures. 



Fig. 55- 



Fro. 56. 



Fig. 55. — Right foot of Emeu, a, astragalus; d^ — ^4, second, third, and fourth 



digits ; 711., metatarsals anchylosed together except at their distal ends ; t, tibia, 



^2, distal tarsal element. 

 Fig. 56. — Left foot of a Monitor Lizard (Varanus). f, fibula; w^ — w«5. the five 



metatarsals, ;«' being that of the hallux ; /, tibia ; i, astragalo-calcaneum ; 



2, cuboides ; 3, ecto-cuneiforme. 



There are other matters, however, more important 

 than this. It has been remarked that the wrist shows 

 an amount of resemblance to the same part in beasts 

 which is wanting in most reptiles and in all birds. 



