430 Mr . Hunter’s Obfervalions on the 
water is fometimqs very often five ; but all this 1 only give 33 
conjecture. 
If the above folution is juft, then only thofe which have the 
organ of fmell can ipout, a fa£t worthy of enquiry. 
The organ of fmell would appear to be lefs neceflary in thefe 
animals than in thofe which live in air, fince fome are wholly 
deprived of it ; and the organ in thofe which have it is ex- 
tremely fmall, when compared with that of other animals, as 
well as the nerve which is to receive the impreflion, as was 
obferved above. 
Of the Senfe of Hearing . 
The ear is conftru&ed much upon the fame principle as in the 
quadruped ; but as it differs in feveral refpe&s, which it is ne- 
ceflary to particularife, to convey a perfect idea of it the whole 
fhould be defcribed. As this would exceed the limits of this Pa- 
per, I fnall content myfelf with a general delcription, taking 
notice of thofe material points in which it differs from that of 
the quadruped. 
This organ confifts of the fame parts as in the quadruped ; 
an external opening, with a membrana tympani, an Eufla- 
chian tube, a tympanum with its procefles, and the fmall 
- bones. There is no external projection forming a funnel, but 
merely an external opening. VVe can eaflly aflign a reafon 
why there fhould be no projedting ear, as it would interfere 
with progreflive motion ; but the reafon why it is not formed 
as in birds, is not fo evident ; whether the percuffions of wa- 
ter could be collected into one point as air, 1 cannot fay. The 
tympanum is conftru&ed with irregularities, fo much like 
thofe of an external ear, that I could fuppofe it to have a fimi- 
lar effect. 
The 
