420 



Mr. H. J. Watt. 



followed appropriately by the song thrush. By this method of calculation 

 the ducked-billed platypus, which has a cochlea of approximately avian 

 type, shows an index of only 2 - — the lowest in the Table. 



Table V. 



: 8 



No. 



' ,63 . : 

 . >74 



68^ ' 

 70 I 



„ 64 i 



57* 



56 

 54 

 66 

 67 

 62 

 73 



Animal. 



Sparrow Hawk 



Song Thrush. 



..Slender-billed Cockatoo 



. Crowned Crane 



•Crowned Pigeon 



Burrowing Owl 



Cape Gannet 



G-reat Tinamoa 



Night Heron 



' Cormorant 



Red-throated Diver 



Apter yx 



Ostrich 



Eed Grouse 



Porphyria 



Buzzard 



Carrion Crow 



Index of 

 basilar 

 membrane. 



C. General Remarks. — How do these results modify the generally accepted 

 notions regarding the mode of action of the cochlea ? The chief point is that 

 they clear up our ideas. The cochlea, it may be said, has usually been 

 vaguely apprehended as a curious organ, and, like the seusations it yields, 

 rather unique in its nature. But just as a renewed psychological analysis 

 of the sensations of sound brings them into clear accord with the structure 

 of the sensations of the other senses,* so this study brings the cochlea 

 morphologically into line with the eye. Each is an organ in which certain 

 main relationships hold universally, with minor variations for special 

 purposes. The cochlea is perhaps more dependent upon the gross bulk of 

 the organism than is the eye. 



Little is yet known directly about the auditory functions of the different 

 animals. But the series given under " Animal " in Table IV seems more 

 acceptable as an indication of auditory power than that formed by increase 

 in the absolute length of the basilar membrane. We should hardly expect 

 the finest hearing in the whale, the seal, (the tiger), the 'grey seal, the 

 dromedary, (the capybara), the horse, (the aard-wolf, man ?), and the sea- 

 cow — which is the order of decreasing cochlear dimensions. And the close 



* Cf. my 'Psychology of Sound,' Cambridge, 1917. 



