Pakker. — Retinal Pigment of Gammarua. 



EXPLANATION OF THE PLATE. 



All the figures were taken from preparations of the eyes of Gararaarus ornatus 

 M.-Edw. They were drawn with the aid of an Abbe' camera, and are magnified 

 570 diameters. 



ABBREVIATIONS. 



cl. cm. Corneal hypodermis. 



cl. rtn/ Retinular cell. 



cl. sn. Accessory pigment cell. 



con. Cone. 



crn. Corneal cuticula. 



/br. r. Retinal nerve fibre. 



mb. ba. Basement membrane. 



nl. rtn.^ Nucleus of retinular cell. 



nl. sn. Nucleus of accessory pigment cell. 



rhb. Rhabdome. 



Fig. 1. Longitudinal section of an ommatidium, showing the arrangement of pig- 

 ment due to exposure to bright light. 



Fig. 2. Transverse section of a retinula from such a preparation as that sliown in 

 Figure 1, and taken near the level marked rhb. in that figure. 



Fig. 3. Longitudinal section of an ommatidium showing the arrangement of pig- 

 ment due to the absence of light. 



Fig. 4. Transverse section of a retinula from such a preparation as that shown in 

 Figure 3, and taken near the level marked rhb. in Figure 1. 



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