THE 



EDINBURGH 

 JOURNAL OF SCIENCE. 



Art. I. — On the Limits of the Retina in the Eye of the 

 Sepia Lolig'o, one of the Cephalopodous Mollusca. By 

 Doctor Knox, F.R. S.E. Lecturer on Anatomy and Phy- 

 siology, and Conservator of the Museum of the Royal Col- 

 lege of Surgeons. (Read to the Royal Society of Edin- 

 burgh.) 



It is well known to those acquainted with the Anatomy of 

 the Mollusca, and with the inestimable writings of Cuvier, 

 that a dark coloured pigment assuming the form of a mem- 

 brane, is interposed between the vitreous humour and retina ; 

 and that this, together with other peculiarities in the eyes 

 of the larger species of the cephalopodous mollusca, viz. their 

 great size, the absence of a cornea and aqueous humour, the 

 peculiar structure of the crystalline humour, the vast number 

 of nerves contributing to form the retina, &c. has excited 

 strongly the attention of all comparative anatomists since the 

 publication of the celebrated Biblia Naturce by Swammer- 

 dam. But, of all these peculiarities, there is none so remark- 

 able as the interposition of this thick dark pigment between 

 the vitreous humour and the retina, presenting as it were 

 a physical obstacle to the passage of the rays of light, on 

 their way to reach the sensitive membrane. This supposed 

 exception to the general laws, agreeable to which the eye- 

 bull of all known vertebral animals has been constructed, ap- 



VOt,. III. NO. II. OCTOBER 1825. N 



