PARKER. — Compound Eyes in Crustaceans. 
66 
a LN 
12. 
13. 
14. 
15. 
16. 
Nile 
5 iteh 
19. 
PLATE II. 
Argulus. 
(Figs. 11-17.) 
A section in a plane transverse to the chief axis of the body and through 
the right eye. Depigmented. x 140. 
A longitudinal section of an ommatidium. % 475. 
A longitudinal section of an ommatidium which had been depigmented. 
The numbers at the left of the figure correspond to the numbers 
of the four following figures of transverse sections, and mark the 
levels at which the latter were made. X 475. t% 
A transverse section through the distal end of a cone and the surround- 
ing pigment cells. X 475. 
A transverse section through the proximal portion of a group of four 
cone cells. The intercellular membranes of the cells present four 
thickened regions. > 475. 
A transverse section through the rhabdome. Depigmented. » 475. 
A transverse section through the retinula somewhat proximal to the 
rhabdome. X 475. 
Pontella. 
The left lateral eye seen from the left side. The section is an optical 
one; its plane is very nearly parallel to the sagittal plane of the 
body. Depigmented in alcohol (see p. 78). XX 275. 
A transverse section of the optic nerve from a region immediately poste- 
rior to the retina. The sagittal plane divides the nerve into sym- 
metrical halves; the fibres in each half belong exclusively to the 
lateral eye of the corresponding side. X 400. 
