214 WHALES, PAST AND PRESENT xv 



of hearing in its essential structure is entirely mammalian, 

 having not only the sacculi and semicircular canals common 

 to all but the lowest vertebrates, but the cochlea, and 

 tympanic cavity with its ossicles and membrane, all, however, 

 buried deep in the solid substance of the head ; while the 

 parts specially belonging to terrestrial mammals, those which 

 collect the vibrations of the sound travelling through air, the 

 pinna and the tube which conveys it to the sentient structures 

 within, are entirely or practically wanting. Of the pinna 

 or external ear there is no trace. The meatus auditorius is 

 certainly there, reduced to a minute aperture in the skin like 

 a hole made by the prick of a pin, and leading to a tube so 

 fine and long that it cannot be a passage for either air or 

 water, and therefore can have no appreciable function in 

 connection with the organ of hearing, and must be classed 

 with the other numerous rudimentary structures that whales 

 exhibit. 



The organ of smell, when it exists, offers still more 

 remarkable evidence of the origin of the Cetacea. In fishes 

 this organ is specially adapted for the perception of odorous 

 substances permeating the water ; the terminations of the 

 olfactory nerves are spread over the inner plicated surface of 

 a cavity near the front part of the nose, to which the fluid 

 in which the animals swim has free access, although it is 

 quite unconnected with the respiratory passages. Mammals, 

 on the other hand, smell substances with which the atmo- 

 sphere they breathe is impregnated ; their olfactory nerve is 

 distributed over the more or less complex foldings of the 

 lining of a cavity placed more deeply in the head, but in 

 immediate relation to the passages through which air is con- 

 tinually driven to and fro on its way to the lungs in 

 respiration, and therefore in a most favourable position for 

 receiving impressions from substances floating in that air. 

 The whalebone whales have an organ of smell exactly on 

 the mammalian type, but in a rudimentary condition. The 

 perception of odorous substances diffused in the air, upon 

 which many land mammals depend so much for obtaining 

 their food, or for protection from danger, can be of little 

 importance to them. In the more completely modified 



