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VIII. On the Development of the Retina and Optic Nerve, and of the Membranous 
Labyrinth and Auditory Nerve. .Sj/ H enry Gray, M.R.C.S. Communicated by 
W. Bowman, F.R.S., Professor of Physiology and of General and Morbid Ana- 
tomy in King’s College, London. 
Received October 18, 1849, — Read January 31, 1850. 
XhE following observations, which I have ventured to offer to the Royal Society, 
are intended to demonstrate the mode of evolution of the essential parts of the visual 
and auditory apparatus. 
In the first part I have considered the mode of development of the optic nerve and 
retina, and also of the various layers of this membrane. In the second part, I have 
traced the evolution of the membranous labyrinth and auditory nerve. Many of these 
observations have not (as far as I am acquainted) been previously made, at the 
same time they will, I think, confirm in a remarkable manner the account that has 
already been given of the structure of these parts*. 
In the minute and accurate account of the structure of the retina which Mr. Bow- 
man has lately given in a series of lectures on the Anatomy of the Eye, he has shown 
that this essential part of the visual organ “ is a nervous sheet containing nearly all the 
structural elements that are found in any part of the nervous system, consisting of an 
unbroken sheet of gray nervous matter, continuous by its fibrous internal surface with 
the axes of the tubules of the optic nerve, and having its external surface formed by 
a structure similar to that of the cineritious substance of the cerebral hemispheres. 
Its permeation by a close network of capillaries assimilates it still further to the gray 
nervous matter, for which reasons it may be considered as a portion of the cerebrum 
advanced towards the surface of the body in a suitable relation to a dioptric appa- 
ratus for the reception of rays of light from external objects.” 
The following observations are intended to demonstrate the evolution and mode 
of development of this membrane in the embryo chick, and they will, I think, con- 
firm in a most striking manner the account that has been given of the structure of 
this part. 
It is not until the thirty-third hour of incubation that there is any indication of the 
evolution of the retina or of the rudimentary eye. At the thirty-first hour (Plate VIII. 
fig. 1) the cephalic extremity of the embryo is indicated by its presenting a somewhat 
* Some of the observations on the development of the retina may be found in my Prize Essay “ On the Ana- 
tomy and Physiology of the Nerves of the Human Eye,” contained in the Library of the Royal College of Sur- 
geons, but unpublished. 
