IN THE EYES OF CERTAIN REPTILES. S 
In a work just published by De Blainville, a distinct 
and direct allusion is made to a theory, partially supported 
by nature, but which, in the present instance, is not appli- 
cable. 
It is there remarked *, that " the differences which the 
Mammalia present, in the point of view we at present con- 
sider, are always susceptible of being divided into two 
categories ; the one sort, pretty nearly inexplicable, is con- 
nected with what we have called the classical degradation, 
and with the degree of organisation to which the species 
belongs ; the others are evidently in relation with the me- 
dium in which the animal must seek its food, or with the 
time of day during which it is so employed, — or, finally, 
perhaps with the nature and kind of its food." 
I arrange (he continues) in the first category, the sort 
of yellow spot, with a small depression, more or less oval, 
translucid in the middle, around which the retina is some- 
what folded, which may be remarked in this membrane at 
some distance externally from the entrance of the optic 
nerve, in the axis itself of the globe of the eye. It is found 
only in the human species, and in the real apes of the Old 
and New Continent.**' 
Unfortunately for the ingenious theory just quoted, the 
transparent point of the retina or foramen, and the fold of 
the membrane, exist in a class of animals differing widely 
from man, and from the apes of the Old and New Conti- 
nent : the class I allude to is Reptiles. I shall here briefly 
describe the appearances, and the particular species in which 
I have detected so singular an appearance. 
Professor Jameson having requested me to re-examine 
with great care my dissections of the class of Reptiles, and 
• Principes d'Anatom. Com par. p. 375. 
