34 MORGAN. [VoL IX. 
of the eye (Zeiss 2, F) is shown in Fig. 20. The pigmented 
area is indifferently well shown in the figure by the darker 
shading. The bulb at the anterior end of the eye is more 
richly pigmented than the rest of the eye. Towards the hol- 
low of the crescent the eye is clearer than elsewhere. Here 
the ectoderm is at a much lower level than over the rest of the 
apical plate. This represents an invagination of ectoderm into 
the concavity of the crescent. 
Longitudinal sections of the larva cut the eye transversely 
as shown in Fig. 22. The ectoderm dips down suddenly and 
in this region the outer ends of the ectodermal cells are clearer 
than those around the eye. Over the region of the pit the 
cuticle is somewhat separated from the surface of the ecto- 
derm, but this is due to the action of reagents. 
Fig. 21 is the outline obtained by focussing beneath the 
surface of Fig. 20. In the center of the bulb is a triangular 
space and within this another concentric line. The inner 
triangle encloses a space that is found, in serial sections, to 
communicate with the exterior at the base of the invagination 
on the concave side of the eye. Between the two triangles is 
a clear zone marked by faint lines, and outside of the larger 
triangle are found the clear ends of ectodermal cells, that carry 
the pigment in the outermost portions of the cells. 
Cross-sections show us that the bulb lies deep within the 
ectodermal wall, that the central cavity is surrounded by cells 
projecting from all sides towards the center. Some of the 
cells of the eye are, therefore, inverted. 
It seems probable that the zone between the triangles of the 
figure represents the thickened cuticle formed by the inner 
ends of the clear cells. The central cavity is not always 
triangular in outline but is more often irregular. Further 
than this I have not made out the histology of the eye. 
Attempts at maceration of the living specimen were not very 
successful. 
In the early stages of the eye the anterior or bulb end was 
not present, the eye being a simple crescent and the invagina- 
tion on the concave side being scarcely discernible. The 
crescent of clear cells is carried beneath the surface in the 
