AUTHORS’ ABSTRACT OF THIS PAPER ISSUED BY 
THE BIBLIOGRAPHIC SERVICE, NOVEMBER 28 
STUDIES ON THE RETINA 
HISTOGENESIS OF THE VISUAL CELLS IN AMBLYSTOMA 
S. R. DETWILER AND HENRY LAURENS 
The Anatomical Laboratory, Peking Union Medical College, Peking, China, and 
the Osborn Zoological Laboratory, Yale University 
THIRTEEN FIGURES 
INTRODUCTION 
The anatomical features of the visual cells in larval Amblys- 
toma have been described and figured by Laurens and Williams 
(717). According to this account, the retina in larvae of 30 mm. 
possesses characteristic rods and cones in the approximate pro- 
portion of four to three. In their figure (p. 76) and in figure 11 
in this paper the identity of these elements is clearly displayed. 
The rods are quite large with typical cylindrical outer segments 
and pear-shaped nuclei, the latter of which are considerably at- 
tenuated on their inner pole. The cones, of which there are three 
kinds, are much smaller elements characterized by the possession 
of conical outer segments, long myoids, and more or less oval 
nuclei. These nuclei are more deeply situated than are those of 
the rods, which typically comprise the outer cell layer of the 
external nuclear layer, and which project through the external 
limiting membrane for variable distances. 
In looking over some sections of the retinae of young larvae, 
our attention was attracted to the striking similarity of the 
visual cells, all of which possessed conical outer segments and oval 
nuclei, characteristics typical of cones. The general impression 
was received that in early stages of development the visual cells 
are all of one type (cone-like), which later differentiate into the 
two distinct categories of elements which characterize the fully 
developed retina. 
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