1000 
iris, is gathered into numerous beautiful ra- 
diating folds (ciliary plice); these in very 
large eyes, as in the Moon-fish ( Orthugoriscus ) 
for example, are seen each of them to consist of 
two or three minute folds, which, as they run 
forwards, unite into one and terminate in a 
point at the circumference of the iris, but in no 
instance do they project freely inwards as dis- 
tinct processes, so as to resemble the ciliary 
processes of Mammiferous Vertebrata. The 
ciliary plice, as indeed most of the posterior 
surface of the iris,is in immediate contact with 
the membrane of the vitreous humour, to which 
it is intimately adherent; for in Fishes there is 
no posterior chamber of the aqueous humour, 
the anterior segment of the crystalline lens pro- 
jecting in many instances quite through the 
pupillary aperture. 
n a space enclosed between the proper 
choroid and the membrana argentea is a struc- 
ture quite peculiar to the osseous Fishes, for it 
is not met with even in the Chondropterygious 
races.* This consists of a spongy mass of 
irregular form, which partially surrounds the 
entrance of the optic nerve (fig. 532, h), and 
extends for some distance towards the front 
Coats of the eye of the Perch. ( After Cuvier. ) 
Fig. 1, muscles of eye-ball ; a, superior oblique ; 
b, inferior oblique ; 1, 2, 3, 4, recti muscles; i, optic 
nerve, Figs.2 and 3, f, f, f, fatty matter; g, cho- 
roid; A, ‘* choroid gland.” 
of the eyeball. This body, which has been 
absurdly called the choroid gland, is some- 
times divided into two portions; at others 
it assumes a somewhat crescentic form, but 
it is always deficient towards the lower part 
* Cuvier et Valenciennes, Hist. Nat. des Pois- 
sons, tom. i. p. 337, 
PISCES. 
of the eye. Its colour is always a deep red, 
and its tissue is principally made up of 
bloodvessels running transversely in close 
rallel lines. Other vessels issue from it which 
are frequently very tortuous and always much 
ramified; these run into the choroid, where 
they form so dense a network that it was de- 
scribed by Haller as a distinct membrane, and 
has been subsequently named membrana Hal-_ 
leri. The use of the foci 5 choroid = 
has not been fully ascertained ; most 
however, it is essentially composed  ecoctile 
tissue, which by its dilatation and contraction 
may have some influence in accommodating the 
form of the eye to the distance of objects, or 
the varying density of the medium through 
which they are seen. 
The optic nerve in many Fishes (at least — 
among the Acanthopterygii) is made up of a 
broad layer of nervous matter folded upon it- 
self like a fan (fig. 532) and enclosed in a 
fibrous envelope, which is continuous with the 
sclerotic coat of the eye. The nerve enters the 
eye at a point remote from the axis of vision, 
penetrating for the most part by an oblique 
course, so that after having piereed the sclerotic 
it has still a considerable distance to » 
through the substratum of cellular tissue and 
between the masses of the “choroid gland” 
before it pierces the choroid and Ruyschian 
tunics. Its diameter is much diminished at 
the point where it shews itself in the interior of 
the eye, where it appears sometimes as a mere 
point, at others under the form of a round or 
irregular spot, or sometimes represents a straight 
line. It then expands into the retina, which, 
when the nerve is folded, as above described, 
has likewise a plicated ap ce. The re- 
tina, as in other Vecesbane lines all the inte 
nal cavity of the eye as far as the ciliary plic 
thus enveloping the vitreous humour. r, 
Another peculiarity in the structure of the 
Fish’s eye is the existence of an apparatus 
apparently analogous to the marsupium of” 
Birds, which extends from the choroid to the 
back of the lens, passing quite through the 
vitreous humour, to which the name of faleé 
Sorm ligament has been given. This s re 
arises by a broad origin from the inner s 
of the choroid at the back part of the eye, 
extending forwards, following the coneavity 6 
the eyeball along its lower surface, arrives ai 
the ciliary zone and is connected with the bae 
of the capsule of the lens, Its shape is fal 
form, as the name indicates, the convexity ¢ 
the curve being attached along the floor of t 
interior of the eye. In the recent eye it is 
delicate and almost imperceptible membran 
but maceration in spirit by rendering it opac 
reveals it to consist of several layers of cell 
losity, most probably enclosing numerous vé 
sels. According to Cuvier and the young 
Soemmering,* the falciform ligament 
through the retina, which is fissured to let 
through; but an examination of the large ey 
of the Moon-fish after long immersion in sf ri 
* De oculorum hominis animaliumque section 
horizontali commentatio. Fol, Goettinge, 1818. 
