BRISTOL NATURALISTS' SOCIETY 
^_ ^ 
IFrom the Bristol Daily Post, January 8tk, 1866.] 
The usual monthly general meeting was held on Thursday 
evening last, at the Philosophical Institution, and was fairly 
attended by members and visitors. Mr. W. Sanders, F.R S., 
the president, occupied the chair, and, after the transaction 
of the routine business, rose and said that it was his painful 
duty to announce the death of Mr. George E, Roberts, one of 
the corresponding members of the society— a gentleman 
who was well-known for his geological researches in the 
field. The hon. secretary then brought forward several 
donations of books to the library, after which Dr. Henry 
Fripp read a paper " On the vision of the fish, and on certain 
structural peculiarities of the fish's eye," which was illus- 
trated with a number of very beautiful anatomical and other 
diagrams, as well as several fish from the museum of the 
Institution. 
Dr. Fripp commenced with a brief exposition of the general 
sensory endowments of the fish, showing the relative in- 
feriority of the senses of taste, touch, smell, and hearing, 
and the n^arked development of the organ and faculty of 
sight. The singular arrangement of a body without limbs, 
adapted to rapid locomotion by muscles of the trunk, was 
shown to meet exactly the problem of the progression of an 
animal immersed in water, and examples were cited showing 
the extraordinary muscular power developed by various 
fishes. The control and direction of this muscular power 
were considered as mainly dependent on the quickness and 
accuracy of vision. The quantity and quality of sub- 
aqueous light were next commented on, and the 
variation of light in strata of different depths as affected 
by the different states of the surface water, 
e g., their state of rest and motion, purity, &c., 
as also by the state of sunlit or clouded atmos- 
phere, and instances of vision exercised by fish of different 
depths under the surface were given. The position of the 
eye, the direction of line of vision, and the extent of the 
sphere of vision in different species of fish, came next under 
review, and the immobility of the pupil and the optical 
question* connected therewith were explained at some 
leegth, and contrasted with the movements of the iris in 
mammal eyes, the physical advantages gained by change of 
pupilary opening being pointed oat. 
The second part of the paper was devoted to anatomical 
details of structure of the different parts of the eye, each 
coat or tunic of the eye-ball being described and compared 
with analogous parts in the mammal eye. The anatomy of 
the choroid coat, ciliary processes, and iris was given in de- 
tail, and in particular that portion of the vascular distribu- 
tion of the choroid vessels, commonly called "choroid gland," 
was described and illustrated by drawings. Dr. Fripp, after 
briefly stating the views of anatomists upon this point, ex- 
pressed his disbelief in the usual explanations of the function 
of that "choroid gland," and gave reasons for the conclusion 
that the structure was neither glandular nor muscular, and 
that it had no influence on the so-calUd "accommodation" 
of position of the lens to near and distant vision. In con- 
sideriur; the position of the lens, it was shown that no for- 
ward movement of the lens was possible, and also that the 
peculiar hardness and inelasticity of the lens did not admit 
of the explanation of "accommodation" by alteration of 
place or form of its curved surface?, The principle of 
"accommodation," and the mode in which itwastffectel 
in the human eye, were explained and illustrated. 
