IV. VERTEBRATA: REPT1LIA. 



591 



This is intertarsal in character, in that it occurs between the first 

 and second rows of tarsal bones (fig. 636, C). 



MD 



FIG. 620. Viscera of Alligator. (From Wiedersheim.) ED, rectum; If, heart; L, 

 liver; Lg, lung ; M, stomach; MD, intestine; Oe, oesophagus; P, pylorus; Tr, 

 trachea ; ZB, body of hyoid; ZH, its cornua ; *, perforations of hyoid. 



Since reptiles lack even transitory gills, the gill slits are com- 

 pletely degenerate before the young escapes from the egg. Dermal 



