Pakker. — Compound Eyes in Crustaceans. 



PLATE VII. 



Ilfysis. 



Fig. 73. A longitudinal section of an ommatidium. The numbers at the left of 

 the figure indicate the levels at which the sections for Figures 76-89 

 were taken. X 475. 



" 74. The distal face of a corneal facet, cleaned in potash and examined in 

 water. X 475. 



" 75. A transverse section of three ommatidia in the plane of the corneal hy- 

 podermis. X 475. 



" 76. A transverse section through the distal end of a cone. X 475. 



" 77. A transverse section through the proximal end of a cone and the adjoin- 

 ing distal retinular cells. X 475. 



" 78. A transverse section similar to that shown in the preceding figure, 

 except that it is depigmented and stained in Kleinenberg's alum- 

 haematoxylin. X 475. 



Figures 79 to 82 inclusive represent consecutive transverse sections through the 

 region of the proximal retinular nuclei of four adjacent ommatidia. The 

 centre of each ommatidium is indicated by the group of cone cells (cl. con.), 

 and the corresponding ommatidia in different sections are designated by the 

 same Roman numeral. The nuclei around ommatidium II. have been num- 

 bered in Figures 79-81. Figure 79 represents the most distal section, and 

 Figure 82 the most proximal one of the series. 



Fig. 79. The bodies marked x and y are portions of nuclei the rest of which are 

 correspondingly marked in Figure 80. X 475. 



" 83. A transverse section of the four fibres at the distal end of the rod (com- 

 pare p. 102). Depigmented, and stained in Kleinenberg's alum-haem- 

 atoxylin. X 615. 



" 84. A transverse section of the rod at a slightly more proximal level than 

 that shown in Figure 83. Depigmented, and stained in Kleinenberg's 

 alum-hsematoxylin. X 615. 



" 85. A transverse section of the retinula somewhat distal to the distal end 

 of the rhabdome (compare Fig. 90). Depigmented, and stained in 

 Kleinenberg's alum-haematoxylin. X 615. 



" 86. A transverse section from the region between the distal end of the rhab- 

 dome and the proximal end of the rod (compare 86 in Fig. 90). De- 

 pigmented, and stained in Kleinenberg's alum-hasmatoxylin. X 615. 



" 87. A transverse section through the rhabdome and surrounding retinular 

 cells. X 615. 



" 88. A transverse section, at the level of the basement membrane, through 

 the nerve fibres from a single retinula. Depigmented, and stained 

 in Weigert's hematoxylin. X 615. 



" 89. A transverse section through the fibres of the optic nerve at a level mid- 

 way between retina and optic ganglion. Preparation as in Figure 

 88. X 615. 



" 90. A longitudinal section through the basal portion of one and parts of two 

 adjoining ommatidia. Depigmented, and stained in Kleinenberg's 

 alum-haematoxylin. X 615. 



" 91. A section cut in the same plane as that shown in the previous figure, 

 but including only the proximal ends of two rhabdomes. Prepara- 

 tion as in Figure 90. X 615. 



" 92. A cone viewed from the side. Isolated in Muller's fluid and studied in 

 water. X 475. 



