MORPHOLOGY OF ANIMALS 



rda 



Fig. i8. Diagram of Embryonic Aortic Arches and their adult Derivatives in different 

 classes of Vertebrates, all viewed from ventral side. A, Embryonic Aortic Arches of all 

 vertebrates, six pairs (1-6), running from the ventral aorta (fa) between the gill-slits to the 

 right {,rda) and left dorsal aortae which join posteriorly to form the single dorsal aorta 

 (da) ; c, carotid artery going to head ; ta, truncus arteriosus where it issues from the heart. 



B, Bony Fishes (Teleostei) with arches 3-6 preserved, each breaking up in the gill filaments. 



C, Tailed Amphibia (Urodela), arches 3-6 preserved, 3d becoming the common carotids (cc) 

 and 4th, the great arches of the aorta (aa), while 5th and 6th are reduced and the latter 

 gives off a pulmonary artery (p) to the lungs. D, Reptiles, 3rd and 4th arches preserved as 

 in C, 5th arch disappears, 6th becomes pulmonary {p). E, Birds, 3rd arch as in D, 4th 

 preserved only on right side, 5th and 6th as in D. F, Mammals, 3rd arch as in D and E, 

 4th becomes the great arch of aorta {aa) on left, and sub-clavian (j) on right, 5th and 6th 

 as in D and E. (After Boas). 



