the Organ of Hearing in Fijh . j8'i 
like thofs of the ray kind ; in others alfo, as in cod, falmon, 
&c. whole Ikeleton is bone, yet this part is cartilaginous. 
In fome fifh this organ is in part within the cavity of the 
Ikull, or that cavity which alio contains the brain, as in the 
falmon, cod, &c. the cavity of the Ikull projecting laterally, 
and forming a cavity there. 
The organ of hearing in fifh appears to grow in fize with the 
animal, for its fize is nearly in the fame proportion with the 
fize of the animal, which is not the cafe with the quadrupled, 
&c. the organs being in them nearly as large in the growing 
foetus as in the adult. 
It is much more fimple in fifh than in all thole orders of 
animals who may be reckoned fuperior, Inch as quadrupeds, 
birds, and amphibious animals, but there is a regular grada- 
tion from the tirft to fifh. 
It varies in different orders of fifh ; but in all it con fills of 
three curved tubes, all of which unite with one another; 
this union forms in fome only a canal, as in the cod, fal- 
mon, ling, &c. ; and in others, a pretty large cavity as in the 
ray kind. In the jack there is an oblong bag, or blind procefs, 
which is an addition to thofe canals, and which communicates 
with them at their union. In the cod, &c. this union of 
the three tubes Hands upon an oval cavity, and in the jack 
there are two of thole cavities; thefe additional cavities in 
thefe fifh appear to anfwer the fame purpofe with the cavity- 
in the ray or cartilaginous fifh, which is the union of the 
three canals. 
The whole iscompofed of a kind of cartilaginous fubftance, 
very hard or firm in fome parts, and which in fome fith is 
crufted over with a thin bony lamella, lo as not to allow 
them to collapfe ; for as the Ikull does not form any part of 
o thole? 
