The Retina and Optic Ganglia in Decapods, especially in Astacus. 73 
Fig. 62. Diagram showing the position of the cells in the transverse aspect 
of an ommatidium of the simpler type. 
Fig. 63. Diagram illustrating the necessary change in position and the 
division of cells in passing from the simpler to the more complex 
type. The planes of division are indicated by dotted lines. 
Fig. 64. Longitudinal section of an ommatidium of the more complex type. 
For the sake of simplicity the fibres of the distal retinular cells 
(blue and gray) are not carried proximally farther than the distal 
ends of the proximal retinular cells. 
Fig. 65. Transverse section of an ommatidium of the more complex type 
at the level of its cone. 
Fig. 66. A similar section at the level of the ihabdome. 
