464 SHAFER 



13, A, and 14, A. Beneath the corneal lenses and lying above 

 the distal ends of the pseudocones is a distinct hypodermal 

 layer. In longitudinal section, two apparent nuclei are present 

 above each pseudocone, sn (Figs. 13 and 14, A). The pseudo- 

 cone itself has a structure similar to that of Sympetrium, its upper 

 part showing still the boundaries of 4 cells which may be seen 

 in cross-section (Fig. 13, C). 



Each retinula is made up of 4 retinular cells which enclose a 

 single rod-like rhabdome, rb (Figs. 13, A and B, and Figs. 



14, A and B). The retinular cells of the ommatidia from the 

 2 extreme parts of the eye described vary, somewhat in shape (as 

 seen in Figs. 13, B, and 14, B) but there are always the 4 cells 

 present, each with its nucleus (Fig. 13, B). Extending up be- 

 tween the different retinulas and lying parallel with them are 

 many open spaces or lumina (Fig. 13, A, I). The smaller ends 

 of these extend even between the distal parts of the pseudocones 

 and their surrounding pigment cells (Fig. 13, C, I). The iris 

 pigment of this eye occupies cells of 2 types called by Grenacher 

 and others the primary or chief pigment cells and the secondary 

 pigment cells. Two primary pigment cells surround the small 

 proximal end of each pseudocone (Figs. 13 and 14, A, cifi). 

 These cells are shown as they appear in cross-section in Fig. 

 13, D, cfi. The nuclei of these cells have not been satisfactorily 

 seen although the nuclei of the retinular cells and secondary pig- 

 ment cells in the same sections were deeply stained and easily 

 seen. Eight to 10 pigment cells have been counted around 

 each pseudocone. They are longer and more slender than the 

 primary cells around which they lie, and they extend down a 

 little between the distal ends of the retinulas (Figs. 13 and 14 

 A, nsp). As has already been said, the pigmentation of the 

 smaller outer elements of the eye occupies the whole length of 

 the retinulge. This pigment lies in the retinular cells themselves, 

 and it is densest always in the distal half of the cells. 



BIBIO HIRTUS Goef. 



The compound eyes of the male Bibio are much larger than 

 those of the female. They nearly touch along the narrow front 

 and occupy almost the entire head. The whole facet area is 



