Parker. — Coiupouud Eyes in Crustaceans. 



PLATE III. 



Ponlella. 



Figs. 20-29. A complete series of ten consecutive sections through the right and 

 left retinas in planes parallel to tlie horizontal plane of the animal. 

 The sections are viewed from their dorsal faces. Figure 20 represents 

 the most ventral section ; Figure 29, the most dorsal. Tlie plane of 

 Figure 25 is approximatelj' indicated by the incomplete dotted line 

 7HW. con. in Figure 18 (Plate II.). In the sections on the present plate 

 the different bodies in the left retina have been designated by appropri- 

 ate letters and figures. The eight rhabdomeres have been indicated 

 simply by numbers; the same number always refers to the same 

 rhabdomere. For the sake of distinction, the two cone cells have 

 been marked d. con. 1 and d. con. 2. Some of the nerve fibres 

 {n.fbr. 7 and n. fbr. S) have been numbered in reference to the par- 

 ticular rhabdomeres with which they are associated. X 400. 



