20 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
reference to the long axes of the cells is shown to exist. Figure 5 
(Plate 1) gives a fair general idea of a frontal section taken at a plane 
about midway between the nuclei of the median cells of the dorsal 
and middle groups. Even with the irregular and ragged appearance 
of the interior bodies (pha’so.) in the cells at the anterior edge of the eye, 
it is plain enough that they have a definite orientation in relation to 
the long cell-axes. Likewise, in the central cell there is a similar 
arrangement of the rod-like structures, which lie in a direction parallel 
to the line joining the anterior and posterior angles of the cell outline. 
Inspection of Figure 2 will show that in this case, also, the conditions 
are similar. 
In the ventral eye, frontal sections give the best idea of the arrange- 
ment of the interior bodies in the retinal cells. Figure 8 (Plate 1) 
shows, in its general features, the condition that appears in all cases. 
The interior bodies are arranged with reference to the long axes of the 
cells, except in the case of the anterior paired cells. This arrange- 
ment is least apparent in the central retinal cell, but this is the cell in 
which the ‘‘sides” are more nearly equal than in any other. Sagittal 
(Plate 1, Fig. 6) and cross sections (Plate 1, Fig. 7; Plate 2, Fig. 23) 
show that there is a somewhat similar disposition of the interior bodies 
as regards the dorso-ventral axes of the cells. 
In preparations of the entire eye, the interior bodies may be seen 
to have the same arrangement that is shown in sections. Figure 1 
shows this in a rather vague way for the lateral eyes. But in Figure 
21 (Plate 2), where the representation of the interior bodies is believed 
to be accurate, as far as they are shown, their arrangement in the 
ventral eye is much like that shown in Figure 8 (Plate 1), particularly 
as regards the anterior cell. In the other cells of the eye, especially 
the paired ones, the arrangement corresponds in a general way to that 
in Figure 8. All the interior bodies that could be seen in the retinal 
cells of the ventral eye have been shown in black. 
The definite arrangement of the interior bodies with reference to 
the long axis of the cells appears in general, and in every cell, in any 
preparation. But if the attempt is made to discover whether every 
interior body is so arranged, it will be seen that there are many ex- 
ceptions; and some such appear in all of the figures. It is possible 
that such exceptions may be more apparent than real, owing to the 
plane in which a section is cut, but they are none the less difficult of 
explanation. ‘There can be no doubt, however, as to the general facts. 
The correspondence in arrangement that appears in cross and 
sagittal sections of the eyes, leads one to question whether the interior 
