116 PATTEN. [VoL. II. 
ably elongated, the latter assuming a figure-8 shape, and the 
former being reduced to an elongated ridge composed of a 
double row of nuclei (Figs. 1-6). The explanation of surface 
views given in the description of eye V. will serve equally well 
here. 
In both eyes I. and III. there are two broad and poorly de- 
fined light areas, one on the dorsal and the other on the ventral 
side of the eyes, which extend almost their whole length. These 
areas are well developed in the stages shown in Figs. 5 @ and 4. 
But they soon disappear, and the eye assumes the appearance 
shown in Fig. 6a. 
Although this eye is considerably longer and larger than eye 
V., it is evidently constructed on the same plan. The figure-8 
shaped clear area is composed, as in eye V., of four sensory 
pits. In the centre is the elongated ridge, and on either side 
of its anterior end is a small, round, dark spot, surrounded by a 
faint depression. In surface views we see that the dark area is 
bent in the middle, and at the apex of the bend, which is directed 
dorsally, is situated the large nucleus. In some cases this con- 
figuration of the dark area is more conspicuous than that shown 
in Fig. 6a, which represents about the average condition. This 
bend is similar to that in the retinal furrow of eye IV., to be 
described later, but it does not, as in this last case, remain 
throughout life. The invagination and general structure of the 
eye is almost exactly like that of eye I’, only it has no dorsal 
appendage or vertical retina. See zufra. 
Eve L. 
The early stages of this eye, which arises from the first 
segment of the optic plate, are much like those of eye III. 
After the light area has assumed a figure-8 shaped contour, it 
increases in extent at the anterior end until a large oval patch, 
in reality a shallow depression, is formed. This depression is 
' finally separated from the remainder of the clear area by a dark 
ridge, leaving only a narrow connecting streak on the ventral 
side of the eye. Figs. 11-16 represent surface views of the first 
segment as seen from the anterior dorsal side of the embryo. 
In Fig. 13 a light streak, or furrow, is seen on the ventral side 
of the eye, united at its anterior end with the main clear area. 
At this point appears a round dark area (d. a.* Fig. 14). 
