THE 
LONDON ano EDINBURGH 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[THIRD SERIES.) 
JANUARY 1836. 
I. On the Retina and Pigment of the Eye of the Common Cala- 
mary (Sepia Loligo). By'THomas Wuarrton Jones, Esg.* 
JN the eye of the Cuttlefish tribe, the retina is said to be si- 
tuated behind a thick layer of dark pigment. As such a 
structure would have the effect of intercepting more or less 
completely the rays of light, the strangeness of it has particu- 
larly attracted the attention of the physiologist and optician. 
The eye in the Cephalopodous Mollusca presents several ano- 
malies when compared with that of the Vertebrata, but I am 
inclined to think that the structure just mentioned is not one 
of them. This is at least the case in the eye of the Sepza 
Loligo, which I have carefully examined ; and what is found in 
one species probably also exists in the other genera and species 
of the order. 
My dissections and microscopical examinations of the eye 
of the SepiaLoligo show, that what has hitherto been described 
as pigment is in reality not so, but a nervous expansion of a 
peculiar texture, tinged of a reddish brown colour—a circum- 
stance which has given rise to the error of supposing it merely 
pigment. Before describing the structure of the retina, it will 
not be out of place first to notice the optic nervous apparatus, 
which differs remarkably from what is observed in the Verte- 
brata. In connexion with the cerebral ganglion, on each side, 
is a large nervous mass, or ganglion, from which fibrils pro- 
ceed in a peculiar manner to the eyeball. On either side of the 
nervous mass, or optic ganglion as it may be called, the fibrils 
* Communicated by the Author. 
Third Series. Vol. 8. No. 43. Jan. 1836. B 
