xii. iQ 



(335) 



Uroddd, larva 



FlG. 198. Diagrams illustrating development and fate of aortic arches in Amphibia, 



left-side view completed. Vessels carrying most arterial blood white, most venous 



blood black, and mixed blood stippled. 



a 1-6 , Primary arterial arches; ca. conus arteriosus; cb. carotid gland; cc. common carotid; 

 da. median dorsal aorta; db. ductus Botalli; dc. left ductus Cuvieri; ec. external carotid; 

 eg. blood-supply to external gill; ic. internal carotid; la. left auricle; Ida. lateral dorsal 

 aorta (d. obliterated part, ductus caroticus); Ig. lung; oph. ophthalmic; or. orbital; pa. 

 pulmonary artery; pea. pulmo-cutaneous arch; pv. pulmonary vein; s. closed spiracular slit; 

 sa. systemic arch; sv. sinus venosus; tra. truncus arteriosus (ventral aorta); v. ventricle; 

 vci, vena cava inferior. (From Goodrich.) 



forwards between the lungs and a large pair of sacs (or a single median 

 sac), the vocal pouches, formed below the mouth. These also serve as 

 resonators, and are developed only in the male. 



19. Circulatory system of Amphibia 



The venous and arterial systems arc less fully separated in Am- 

 phibia than in lung-fishes. The auricles are completely divided by an 

 inter-auricular septum, venous blood returning to the right, arterial 

 to the left auricle. There is only a single ventricle, but this is provided 

 with spongy projections of its wall, which may prevent the mixing of 

 the blood. The ventral aorta (conus arteriosus), springs from the 



