TRANSACTIONS OF THE SECTIONS. ll 
a larger sphere, and the posterior that of a smaller sphere* ; and he adds, what is not 
correct, that “ the lens presents the same denticulated fibrous structure, arranged in 
concentric laminz, as in the higher animals.’’ Siebold+ gives nearly the same 
account of the crystalline, the lens being spherical, and the anterior of its two halves 
less convex than the posterior. Mr. Wharton Jones considers the lens as ‘a sphere 
divided into two unequal segments, an anterior smaller and a posterior larger f.”’ 
In studying the crystalline lenses of animals about twenty-five years ago, I had 
occasion to examine several lenses of the Cuttle-fish, but having found a consider- 
able difference in the structure of different lenses, and not knowing the species from 
which they were taken, I did not publish my observations in the memoirs which I 
sent to the Royal Society in 1833 and 1835. As the subject, however, is a very 
interesting one, and as the attention of anatomists has been lately directed to the 
structure of the crystalline lens, I have ventured to submit to the Section a short 
account of my observations. 
In the greater number of lenses which I have examined, and which I believe were 
those of the Sepia Loligo, the lens was not a sphere, as maintained by the greater 
number of the anatomists to whom I have referred, nor did it consist of two spherical 
segments of unequal convexity. Its posterior and larger portion was decidedly a 
paraboloid, and its anterior and smaller portion a spherical meniscus, whose concave 
surface coincides with the convex surface of the section of the paraboloid. This re- 
markable form of the lens is represented in fig. 1, where ABC is the axis of the lens, 
ADCE a section of the whole lens through the axis, DBE the convex surface of 
the paraboloid, which is spherical, and MNOP (fig. 2) the spherical meniscus, whose 
Fig. 1.—The whole lens. Fig. 2.—The anterior lens. 
on M 
A Cc 0 Ee 
N 
BE 
concave surface MON has the same curvature as DBE, the anterior face of the 
paraboloid. 
The following are the dimensions of the various parts of t/ree lenses :— 
inch. First lens. 
AB=0°3433, DE=0°51, AC=0°433. 
MN=0'333, BC=OP=0:09. 
Second lens. 
AB=0°333, DE=0'50. 
Third lens. 
AB=0'30, DE=0°457. 
In some indurated lenses I have found the spherical surface MON slightly con- 
vex, and the corresponding surface DBE similarly concave; but I cannot decide 
whether this structure is abnormal, or that of lenses belonging to different species of 
the Cuttle-fish. That it was not produced by induration, will appear from the 
following description of indurated lenses which have been in my possession for 
twenty-five years, in all of which the faces DBEare convex, and the faces MON concave. 
1. AB=0°29, DE=0°433. 
2. AB=0'235, DE=0°37. 
3. AB=0'19, DE=0-27. 
* This description is inconsistent with the drawing (fig. 224), which represents the whole 
lens asasphere. In this figure the central part of the lens is represented as not lamellar as 
its structure. 
fT Anatomy of the Vertebrata, p. 283. Boston, 1854. 
} Phil. Mag. Jan, 1836. vol. viii. p. 1. 
