EYE OF THE CUTTLE-FISH. 593 



surface of the crystalline lens (o) is found quite naked beneath it, 

 neither an aqueous humour, nor an iris properly so called, being pre- 

 sent. The outer coat of the eye (g g, i) represents the sclerotic tunic 

 in Man : it is tough, fibrous, and of a silvery lustre ; perforated ante- 

 riorly by a large round aperture, representing that which contains the 

 cornea in the human eye, and pierced posteriorly by numerous foramina, 

 through which the multitudinous branches derived from the optic gan- 

 glion (&) enter. 



Fig. 292. 



Anatomy of the eye of the Cuttle-fish. (After Cuviev.) 



(1590.) The second tunic is usually regarded as the retina, occupying 

 a singular situation and presenting a very anomalous structure. No 

 choroid intervenes between this retina and the sclerotic, as is the case 

 in the eye of Man ; but numerous nervous branches given off from the 

 optic ganglion (&), having penetrated into the interior of the eye through 

 the cribriform sclerotic, immediately expand into a thick nervous mem- 

 brane which lines the sclerotic tunic, and is continued forward to a deep 

 groove in the substance of the crystalline lens, wherein it is implanted, 

 so as to form a kind of ciliary zone (m), which is slightly plicated, and 

 obviously assists in keeping the lens in situ. 



(1591.) Between the retina and the vitreous humour is interposed a 

 thick layer of black pigment, which, being thus strangely situated, has 

 very naturally puzzled all physiological inquirers, inasmuch as it would 

 apparently form an insurmountable barrier between the rays of light 

 and the retinal membrane. The researches of Professor Owen would 

 seem, however, to have removed the difficulty presented by this hitherto 

 incomprehensible and anomalous arrangement, as he has succeeded in 

 discovering, in addition to the thick post-pigmental nervous expansion, 

 a delicate lamella in front of the pigmentum nigrum, correspondent, in 

 position at least, with the retina of vertebrate animals. " In the eyes of 



