AMPHIBIA 



295 



Circulatory System. — It is very easy to see in the embryonic 

 Anura and even in the adult Urodela a transition from the fish type 

 of vascular system. The red blood corpuscles of the Amphibia are 

 oval, nucleated and extremely large. In the salamander Amphiuma, 

 the red corpuscles are eight times as large as those of a man. 



i/enfr/c/e 

 Superior \/ena co\/a y '^. 



Innominate 1 



Internal Jugular - - 



Brochiol- 



Posterior corc/mol- 



Splenic 



~ — ^ — inferior gastric 



Pancreatic 



Portal 



Atx/ominol 



■Mesenteric 

 Inferior cava 



Vein of Jacobson 



Prom urinary ■ 



I Hoc 

 Caudal - 

 Fig. 159. Venous system. Ventral view. (After Reese, Amer. Nat., 1906, vol. 40.) 



Urinogenital Organs. — In the male amphibian, we find an inter- 

 esting condition in that the " Leydig's duct " transports both urine 

 and sperm to the cloaca. 



Embryology. — The ripe ova of frogs have distinct po/ar dif- 

 ferentiation. The upper " animal pole " is deeply pigmented, while 



