ESTERLY: EUCALANUS. 25 
section is unfavorable, it is practically impossible to trace the indi- 
vidual nerves. 
As previously stated, the optic nerve leaves the central (or pigment) 
cell of the eye at its posterior border, the axis cylinders having 
passed through that cell in their course from the visual cells of the 
eye. ‘The fibres can enter the pigment cell only at the points where 
the optic cups are in contact with the central cell. Figure 2 (Plate 1) 
shows that the lateral optic vesicles are separated from the tapetal 
layer of the pigment cell everywhere (at the level of the section) except 
at the anterior angle of the anterior basal plate and at the posterior 
angle of the posterior plate, and that in these places the tapetum is 
interrupted. In cross sections (Plate 5, Figs. 49, 50), it can be seen 
that the lateral eyes (Plate 5, Fig. 49) are in contact with the central 
cell (cl. c) at the dorsal and outer ventral margins of the latter; and in 
serial cross sections it is shown that the eyes touch the central cell 
along its entire dorsal and ventral margins, for in no section of such 
series are these connections broken. But it should be said that where- 
ever the lateral eyes and central cell come in contact, the surrounding 
capsular membrane of the eye vesicle is present. I believe that the 
spaces separating the eyes from the central cell (Plate 1, Fig. 2; Plate 4, 
Figs. 49, 50) are not artifacts due to shrinking, because they occur 
in every preparation, no matter what the treatment may have been, 
and in all preparations the conditions are precisely as described. 
Again, it seems reasonable to maintain that, if the spaces were due to 
shrinkage, there would be evidence to this effect in wrinkling or 
irregularities of outline, but this is not the case. | 
In the ventral eye, the relations of the central cell and optic cup are 
similar to those described for the lateral eyes. Figures 6 (Plate 1), 
44 and 48 (Plate 5) show that the two are in contact at the anterior 
and posterior margins of the eye and also at a point midway between 
the two. As in the paired eyes, the tapetum (fap.) is interrupted where 
the eye touches the pigment cell (cl. c). ‘These anterior and posterior 
regions of contact also mark the anterior and posterior limits of the 
basal plate of the eye, but the other place of contact is through an 
opening in the basal plate, the plate being continuous lateral to the 
region of contact, as it is anterior and posterior to it. (Compare 
Plate 1, Fig. 6, and Plate 5, Figs. 49 and 50.) ‘The ventral component 
and the pigment cell (Plate 5, Fig. 49) are also in contact lateral to 
the basal plate (a. ba.) of the ocellus and nerves leave the retinal 
cells at these points. 
As a basis for describing the nerve supply of the eye, we may take 
