306 
FREDA BAGE. 
The structure of the retina of various vertebrates has 
engaged the attention of many workers, especially during the 
last eight or ten years. The greater part of the work (apart 
from that on the human eye) has been done on amphibians, 
while a certain number of papers have also been published 
dealing with birds and fishes. So far as I have been able to 
ascertain very few investigations have been made on reptilia 
of any kind. 
As the literature of the visual cells in vertebrates generally 
has been fully discussed by Howard ( 19 ) as recently as 1908, 
it is unnecessary to enter into historical details in this 
paper. 
A paper dealing with the lateral eyes of Splienodou was 
published by Osawa (23) in 1898. So far as the description 
of the structure of the retina goes, I find that my results do 
not agree with his at all. He begins by stating that, unlike 
other Eeptilia, Sphenodon possesses in its retina both rods 
and cones, and that oil-globules occur in both. His figures 
are very unconvincing and wanting in detail. So far as I 
can make out from them, and from the text, he regards as 
cones only the large flask-shaped cells which are generally 
described as the “near cones” of the “double cones.” He 
says be must leave undecided the question whether or not 
these are to be regarded as “ Hauptzapfen ” (i. e. near 
cones). He figures an oil-globule in the “ Hauptzapfen,” 
which certainly does not exist in the near cones, and he calls 
the paraboloid the ellipsoid. How it is generally admitted, 
by those who have worked at the subject, that the cones of 
certain groups of vertebrates possess oil-globules, but that 
the rods never do. Osawa, however, describes as rods sense- 
cells which possess oil-globules, but are of a somewhat 
different shape and size from those which he figures as cones. 
These so-called rods (Stabchen) are what I shall speak of 
later as ordinary single cones. He also finds some inter- 
mediate forms which he calls “ doubtful cones or rods,” and 
these are probably the small forms which I suppose to be 
small single cones. He states that he finds cones grouped in 
