
PARKER. — Compound Eyes in Crustaceans, 
PLATE X. 
In all Figures on this plate the magnification is 475 diameters. 
Cambarus. 
Figures 118-122 represent a series of five successive transverse sections through one 
and parts of four adjoining ommatidia in the region of their proximal 
retinular nuclei. Figure 118 represents the most distal section in 
the series; Figure 122, the most proximal. In these figures, only 
the outlines of the nuclei and the groups of cone cells are drawn. 
Crangon. 
Fig. 123. A transverse section through a number of ommatidia in the region of 
their distal retinular nuclei. 
Palinurus. 
Fig. 124. A transverse section through a retinula in its middle region. The out- 
lines of the retinular cells cannot be distinguished; the position of 
each cell is marked by an irregular light mass in its centre. 
«© 125. A transverse section through a retinula in the plane of its eighth 
nucleus. Depigmented. 
Cancer. 
(Figs. 126-131.) 
Fig. 126. A corneal facet viewed from its distal surface. The cuticula from which 
this facet was drawn was cleaned by being boiled in a strong aqueous 
solution of potassic hydrate. It was examined in water. 
« 127. A transverse section of the distal end of a cone. 
“ 128. A transverse section through three ommatidia at the level of the distal 
retinular nuclei. The pigment granules have been indicated in only 
the lower circle of cells. 
«‘ 129. A-transverse section through the distal region of four retinule. In the 
two on the right, the pigment granules have not been drawn 
«130. A transverse section through a retinula near the base of the retina. _ 
“ 131. A slightly oblique section through the basement membrane. The upper 
part of the figure represents the retinule as seen in transverse sec- 
tion distal to the basement membrane; the part marked mb. ba. 
represents the region in which the membrane itself appears in section, 
and the lower half of the figure shows the cut fibres of the optic 
nerve. The pigment granules are omitted from the right side of the 
figure. The transition from the retinular cells to the nerve fibres 
is evident in passing over the section from top to bottom. 
