Fig. 24. — A 12-MM. tadpole dissected from the vei^tral 



SURFACE to show THE HEART, THE INTERNAL GILLS, THE BRAN- 

 CHIAL VESSELS, AND THE HEAD-KIDNEYS AND THEIR DUCTS. THE 

 TAIL, WHICH IS ABOUT DOUBLE THE LENGTH OF THE HEAD AND 



BODY, HAS BEEN REMOVED. X 22. (After Marshall.) 



A, dorsal aorta. A F.1^ A ^.3, afferent branchial vessels of first and th'ri 

 branchial arches. A L, Ungual artery. CG, carotid gland. £:A, junction be. 

 tween afferent and efferent branchial vessels of first branchial arch. £ I^'.l^ E /'".3, 

 efferent branchial vessels of first and third branchial arches. G M^ glomerulus. 

 KA^ archinephric or segmental duct. KM^ Wolffian tubules. K P, prone- 

 phros or head-kidney. K S.\y^ A' 5.3, first and third nephrostomes of head-kidney- 

 Z./, upper lip. LJy lower lip. L P^ hind limb. O A^ aperture of opercular 

 cavity. O P^ opercular cavity. RS^ sinus venosus. R T^ truncus arteriosus. 

 R F, ventricle. TC, cloaca. TO^ oesophagus, cut short. T R^ rectal spout. 



66 



