Parker. — Compound Eyes in Crustaceans. 



PLATE IX. 



Palcemonetes. 

 In all Figures on this plate the magnification is 475 diameters. 

 Fig. 103. A longitudinal section of an oramatidium. The numbers at tlie left of 

 the figure correspond to the numbers of nine of the followmg fig- 

 ures of transverse sections, and mark the levels at which the latter 

 were taken. 

 '' 10-4. 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 tlie series; Figure 112, the most proximal. 

 Fig. H-S. A transverse section of the retinula near the distal end of the rhabdome. 

 Depigmented. 

 " 114. A transverse section of four retinulse at tlie level of the eighth retinular 



nucleus. 

 " 115. A transverse section through four retinula? in the region of the accessory 

 pigment cells; viewed by reflected liglit. The retinulae appear as 

 dark masses embedded in a wliitish field composed for the most part 

 ofthe substance of the accessory pigment cells. 

 " 116. A transverse section througii 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. 



