THE ORGANS OF SENSATION 



187 



FIG. 95. Ape. 



FIG. 96. Ape. 



of the first visceral arch, is either completely absent in amphi- 

 bians, reptiles and birds, or, at most, exists only as a rudiment 

 in certain birds (night-birds), being represented by stiff " ear- 

 feathers ". The external ear is barely perceptible, or wholly 

 lacking in the aquatic mammals (Sirenia and Cetacea). Other 

 mammals possess membranous external ears supported by 

 cartilage and folded into varying shapes ; broadly speaking, 

 the form of helix and antihelix can be observed. 



The lower apes, 

 like the majority of 

 mammals, show more 

 or less pointed ears ; 

 it is only in man and 

 the Anthropoids that 

 the concha is round 

 (Figs. 95-98), but both 

 the extent of folding 

 and the size of the 

 cartilage have become 

 greatly reduced. 



A human charac- 

 teristic which is by no 

 means invariably pre- 

 sent is the so-called 

 Darwinian tubercle 

 (see Fig. 99) on the 

 free margin of the 

 helix ; this tubercle 

 was regarded by Dar- 

 win as the analogue of 

 the pointed tip of the 

 ear in animals. Lud- 

 wig Meyer and Langer l objected that if this tubercle really 

 represented the apex of the ear in brutes, it should not be 

 situated somewhere on the middle of the outer border but 

 should lie at the summit of the ear. They are therefore in- 

 clined to regard the tubercle merely as the remains of an 

 interruption of the margin of the helix. If, however, one takes 



1 Ranke, loc. cit., ii., p. 38- 



FIG. 97. Man. FIG. 98. Man. 



(Haeckel, Anthropogenie.) 



