462 SHAFER 



has not been determined. Cross-sections of the retinular-like 

 bodies under the large ommatidia are shown in Fig. 4, B. 

 Regularly, they appear as shown, with 4 cells — one large, 2 

 smaller and 1 very small cell. Cross-sections of the corre- 

 sponding retinula above show that the separate cells there have 

 almost lost their identity in the adult eyes ; but in the very 

 young teneral adult 4 nucleated cells may be seen (Fig. 4, C) 

 in cross-section. From the lower part of the retinular-like bodies 

 extend branching tree-like nerve fibers which break up into 

 brushes of fibrils at their inner ends. 



The pigment of the region of the small ommatidia may be 

 described under 4 heads : 



1. That grouped in dense black masses around the pseudo- 

 cones and already named the iris pigment. It is contained in 2 

 kinds of cells called by Grenacher, 1879, primary and secondary 

 pigment cells. The secondary cells are long, narrow and 

 closely packed around and among the pseudocones — their axes 

 lying parallel with the cone axes. Around cross-sections of 

 the upper parts of the cones 20 to 22 of these pigment cells may 

 be counted in a circle touching the outer boundary of the cone 

 (Fig. 3, B, sip). In the sections near the inner tapering tip of 

 the cone as few as 14 pigment cells have been counted touching 

 the cone. Below that the separate cells could not be counted, 

 but they are packed all the way between the different pseudo- 

 cones, being densest on the middle plane of the cone. There 

 are 2 chief pigment cells for each eye element. They are 

 short and thin and the 2 encircle the cone tip (Figs. 3 and 4, A). 



2. Pigment occupies the retinula and the cells between the 

 retinula from the apex of the cones to the basement membrane. 

 Beginning near the distal ends of the retinula this pigment 

 becomes denser and denser toward the basement membrane 

 until a plane (ee, Fig. 3, A), is reached a little below the mid- 

 dle of the retinula. From this plane to the basement membrane 

 the pigment is again less dense. 



3. A band of dense black pigment lines the basement mem- 

 brane and on the inner side of this membrane, extends down to 

 the distal ends of the retinular-like bodies. It is densest immedi- 

 ately beneath the basement membrane, around the trachea and 



