


PaRKER. — Compound Eyes in Crustaceans. 
PLATE IX. 
Palemonetes. 
In all Figures on this plate the magnification is 475 diameters. 
Fig. 103. A longitudinal section of an ommatidium. The numbers at the left of 
“ec 
the figure correspond to the numbers of nine of. the following fig- 
ures of transverse sections, and mark the levels at which the latter 
were taken. 
104. A longitudinal section of an ommatidium which has been depigmented. 
The bodies marked x resulted from the action of the depigmenting 
reagent. 
105. A facet from the corneal cuticula; cleaned in strong potassic hydrate, 
and examined from its distal side in water. 
106. A transverse section through the region of the corneal hypodermis. 
107. A transverse section through the distal end of a cone in the region of 
the nuclei of the cone cells. 
108. A transverse section through the middle of a cone. 
109. A transverse section through parts of four ommatidia in the region of 
the distal retinular nuclei. 
Figures 110-112 represent three successive transverse sections, each through 
five ommatidia, in the region of their proximal retinular nuclei. Only the 
outlines of the nuclei and the five groups of cone cells (cl. con.) are drawn. 
The nuclei in each ommatidium are numbered from 1 to 7, and as their plan 
of arrangement is the same in the different ommatidia, corresponding nuclei 
have been designated by the same number. In some cases the nuclei were 
cut in two, and consequently appear in two adjoining sections. In such 
cases the two parts have been marked with the same number. Figure 110 
is the most distal of the series; Figure 112, the most proximal. 
Fig.113. A transverse section of the retinula near the distal end of the rhabdome. 
Depigmented. 
114. A transverse section of four retinule at the level of the eighth retinular 
nucleus. 
115. A transverse section through four retinule in the region of the accessory 
pigment cells; viewed by reflected light. The retinule appear as 
dark masses embedded in a whitish field composed for the most part 
of the substance of the accessory pigment cells. 
116. <A transverse section through a retinula at about the same level as that 
shown in Figure 115. Depigmented. 
117. <A transverse section through the optic nerve fibres at a level slightly 
proximal to the basement membrane. Depigmented. 
