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Right Olfactory Organ. 
Anterior Nostril (a. nos.)—A small aperture situated 
on the anterior aspect and almost at the apex of a largish 
tube. _ 
Posterior Nostril (p. nos.)—A large aperture only 
slightly raised above the surface of the body. 
Both nostrils open into a large nasal chamber (n. eh.), 
the external wall of which is perceptibly thickened, and 
the internal wall of which is thrown into a vertical series 
of large folds or olfactory lamine (0. /am.). These 
lamine bear the olfactory cells and sensory hairs, to which 
the olfactory nerve is distributed (. olf.), and run in a 
longitudinal direction. The nasal chamber is therefore 
the sensory chamber of the nose, and in most fishes is the 
only one present. There were 9 olfactory lamin in the 
right nasal chamber in our sections, but the most dorsal 
and ventral one is very small. 
Into the nasal chamber open the nasal sacs, the walls 
of which are non-muscular and non-sensory, but contain 
innumerable goblet cells. They therefore have a secretory 
function at least. These sacs are as follows : — 
Dorsal nasal sac (7. sac.1)—Opens into the nasal 
chamber behind and above. Passes forwards and bifur- 
cates. ‘The inner limb soon terminates, but the outer one 
passes far forwards, and although it is very narrow from 
side to side, it is very wide from above downwards. Its 
true extent therefore does not appear in the figure. 
Antero-ventral nasal sac (n. sac.”).—Has a common 
opening with the postero-ventral sac into the nasal 
chamber behind and below. Its outer wall is continued 
backwards into that of the third sac. Passes far forwards, 
narrow from above downwards, but wide from side to side, 
between the mucous membrane of the mouth and the 
