PARKER, — Retinal Pigment, 
EXPLANATION OF PLATE. 
All the figures were taken from preparations of the eyes of Palemonetes vul- 
garis Stimp. They were drawn with the aid of an Abbé camera, and are all mag- 
nified 335 diameters. 
el, con. 
cl. dst. 
(EDO, 
cl. sn. 
con. 
ern, 
Fig. 1 
Fig. 2 
Fig. 3 
Fig. 4 
Fig. 5 
Fig. 6 
Fig: T 
Fig. 8 
Fig. 9. 
Fig. 10. 
ABBREVIATIONS. 
Cone cell. br. r. Retinal nerve fibre. 
Distal retinular cell. mb. ba. Basement membrane. 
Proximal retinular cell. nl. con. Nucleus of cone cell. 
Accessory pigment cell. nl. ern. Nucleus of corneal hypodermis cell. 
Cone. nl.px. Nucleus of proximal retinular cell. 
Corneal cuticula. rhb, Rhabdome. 
Longitudinal section of an ommatidium, showing the arrangement of 
pigment characteristic for the light. 
Longitudinal section of an ommatidium, showing the arrangement of 
pigment characteristic for the dark. 
Transverse section of a cone from an ommatidium, such as is shown in 
Fig. 2 (dark). 
Transverse section through the proximal processes of the distal retinular 
cells in an ommatidium such as that shown in Fig. 2 (dark). 
Transverse section through the distal retinular cells of an ommatidium 
such as that shown in Fig. 1 (light). 
Transverse section through the retinula (rhabdome and proximal retinular 
cells) of an ommatidium like that shown in Fig. 1 (light). 
Transverse section through two groups of retinal nerve fibres. 
Lateral view of a cone with one of its two distal retinular cells still 
attached. The distal retinular cell shows the condition characteristic 
for the dark. The preparation was isolated from a retina macerated 
in Müller's fluid. 
Longitudinal section through the bodies of two distal retinular cells, 
which show slight foldings accompanying their shortening. The 
preparation was made from an animal which had been kept in the 
dark thirty-eight days and then exposed to light for four hours and 
three quarters. The figure was drawn from preparations made by 
Professor F. H. Herrick, who kindly granted the author the privilege 
of studying them and making drawings from them. 
Longitudinal section through the edges of two distal retinular cells (see 
p. 287), from the same set of sections as that from which Fig. 9 was 
drawn. 
