82 BULLETIN OF THE 
the method of the distribution of the nerve-fibres to the retinal layer. 
It will require a more careful study of maceration-preparations in con- 
nection with sections in different planes to settle this important question. 
It seems to me improbable that the nerve-fibres pass directly through the 
tapetum. From what I have seen, I think that most of them pass 
around the margins of that layer to join the anterior ends of the retinal 
cells, though I have reason to think that some of them reach the retina 
through the fissure in the tapetum. 
The position of the other eyes is not quite so favorable for study by 
means of sagittal sections ; and yet an examination of Figs. 4-6 is suffi- 
cient to show that the infolding does not take place in the same direc- 
tion in both of the lateral eyes. In the anterior laterals the retinal mass 
lies in front of the infolding, whereas in the posterior laterals the retinal 
mass lies, as in the posterior median eyes, behind the infolding. 
In the anterior lateral eye (Figs. 4, 5) the four tracts are readily dis- 
tinguishable ; and it is necessary only to compare Figs. 4 and 5 with the 
later stage in Fig. 15, and the still older one of Figs. 18 and 19, in order 
to learn that the fate of each is the same as in the eye already described ; 
a further description is therefore unnecessary. 
That all the layers — especially that producing the tapetum — are not 
seen with the same distinctness in the posterior lateral eye, is, without 
question, due to the direction of the axis of that eye. The sections are 
cut in a plane which makes a considerable angle with the main axis of 
the eye and of the infolding, and the figures therefore give a more ob- 
lique view of the cells of the tapetal layer, which consequently are not 
so readily distinguishable from those of the retina. The earlier sections. 
(Figs. 4, 5) pass through the fundus,—the last (Fig, 7) through the 
margin of the infolding, where the first and the fourth layers begin to 
merge into one another. (Compare Explanation of Figures.) 
It can be seen from the figures of a later stage (Figs. 13-15) that the 
axis of this ocellus continues to be nearly perpendicular to the sagittal 
plane. Of the three sections, that which is nearest the surface of the 
head (Fig. 13) shows the greater portion of the tapetum,* with its 
median fissure, nearly en face; there are also shown, between the ob- 
server and the tapetum, faintly expressed markings nearly perpendicular 
to the fissure. I could not discover that they were continuous across 
the region of the fissure. They are undoubtedly due to the differentia- 
* A part of the posterior end of this structure was cut away with the preceding 
section. 
