400 pisces. 



upper part of the head, where lies a pulpy substance mixed with a kind 

 of cellular membrane, as it were filled with the mucus: this is the 

 glandular apparatus which secretes it. 



The pupil is not round, but seems to be quadrangular 1 . There is a 

 membrana nictitans, pretty thin and hard, covered by such a skin as 

 that of the animal's body ; but it is not so rough, though becoming 

 rougher towards the edge 2 . Its muscle is a pretty strong one arising 

 from the hind part of the head, and passing round the anterior or 

 rather posterior canthus ; then, passing forward along the under eyelid, 

 it is inserted into the inferior horn of the membrane. The membrane 

 is mostly beneath the under eyelid, not quite at the inner angle as in 

 birds. The motion of this muscle can but bring the membrane over 

 one-half of the eye, excepting the eye is very much depressed : but, as 

 there seems to be little or no motion in the eyelids, this membrane 

 seems to supply their want of motion : indeed, the skin of the eyelids 

 will not allow of any ; and the membrane not being a transparent one, 

 seems to preclude one of its uses in birds ; for they can see in some 

 measure through it, when it is doing its common office. The tunica 

 conjunctiva is very strong. The eye and muscles are surrounded by a 

 fine pulpy substance extremely slippery. The muscles of the eye are 

 four, straight, arising from the bottom of the orbit, and two, oblique, 

 arising from the inner or rather anterior canthus : the superior oblique 

 has not a trochlea. These oblique muscles cross each other, which gives 

 a greater length of muscular fibre 3 . The optic nerve passes into the orbit 

 half an inch from the insertion of the muscles nearer the fore-part 4 . 

 Just by where the muscles arise there is a small stalk fixed, which is 

 very strong and hard in substance, in some cartilaginous ; it passes out 

 towards the eye, and is spread and lost on a glarey substance that is 

 on the bottom of the eye, and among the muscles. This stalk seems to 

 be in the direction of the axis of the eye, and to be the centre of motion 

 of the eye, for the muscles arise nearer to it than to the optic nerve. 

 Just behind the posterior angle of the eye there is an opening [spiracle, 

 ' 1' event' of Cuvier], which I took to be the ear, which passes inwards and 

 downwards, becoming larger and larger, and opens into the mouth just 

 before the first gill. The mouth, or what may be called the lips, is 

 wide, and becomes rather wider inwards. There is a sort of tongue, 

 which seems to be no more than the lower fixtures of the bones of the 

 gills ; this surface is rough, and so is the roof of the mouth. 



The oesophagus is a continuation of the mouth, hardly becoming 



1 [Hunt, Prep. Phys. Series, No. 1670.] 2 [lb. No. 1762.] 



3 [lb. Nos. 1761—1763.] * [lb. No. 1670.] 



