367 



continuation of the middle line sulcus. The naked area is a 

 fine pink colour, and the surface has a finely-granulated 

 texture. The narial slits are bounded above by naked skin 

 for the whole of their length, but the inferior margins are 

 pubescent a short distance from their anterior ends. The 

 infra-narial portion of the rhinarium is marked by a median 

 sulcus, and is continued to the free margin of the upper 

 lip, narrowing rapidly as it approaches the lip. The hair on 

 the supra-narial margin is directed towards the distal end 



D 



C D 



Fig. 7. 



The form of the external ear. 



A, 32 mm. B, 65 mm. C, 80 mm. D, 100 mm. embryos. 



of the rhinarium, whilst on the infra-narial margin the hair 

 direction is reversed. 



The External Ear (see figs. 7 and 8). — In the 32 mm. 

 stage (see fig. 7, A) the auricle is folded with the free tip 

 directed forwards, and the whole pinna is tightly adpressed 

 to the side of the head. In the 45 mm. stage it is folded 

 with the free tip directed backwards, and again the pinna 

 is closely applied to the head. At 65 mm. (see fig. 7, B) the 

 enlarging auricle is not so closely applied to the head, and 

 at 80 mm. (see fig. 7, C) it projects from the side of the 

 head, the direction of folding being now variable. In older 

 examples the free auricle usually has its tip folded forwards 



