DIVIDED EYES OF CERTAIN INSECTS 47 1 



tiny pigment granules being present in some sections. But these 

 may have been carried there by the razor. Upon the basement 

 membrane are short pigment cells which are sometimes above 

 the membrane between the proximal ends of the retinulae ; some- 

 times beneath the membrane between the nerve fibers, nf\ and 

 sometimes partly above, partly beneath the membrane. A 

 second delicate membrane k marks the lower limit of migration 

 of this pigment. 



Fig. 17, A and B, show the structure of two ommatidiae in 

 the lateral pigmented eye of Callabcctis. One of the elements 

 is represented in its normal pigmented condition, the other de- 

 pigmented so that the position of nuclei maybe seen. The cor- 

 neal lenses in this eye are thin as compared with the turban eye 

 and their inner faces fit snugly upon the distal bases of the cones. 

 These cones are not as dense as those of the large elements 

 just described. They are 4 in number, however, and appear 

 to have the same density throughout. The cone cell nuclei en, 

 are found in the extreme distal base of the cone. In depig- 

 mented sections the nucleated distal ends of the retinular cells 

 may be seen touching the tip of the cone. There are 7 of these 

 retinular cells surrounding the rod-like rhabdome as represented 

 in Fig. 17, B. No primary iris pigment cells are present, and 

 there are but half the number of secondary pigment cells found 

 in the turban eye. The 11 cells (Fig. 17, B), which are present, 

 however, are densely pigmented, and they overlap the cones 

 and the upper retinular. The retinular cells are deeply pig- 

 mented through their entire length. Just beneath the basement 

 membrane is a narrow almost transparent granular tapetum and 

 under that an irregular broader band of pigment. So far, this 

 pigment has not been observed above the basement membrane 

 in the lateral eye. Nerve fibers «/"(Fig. 17, A) lead from the 

 inner ends of the retinula through the tapetum and the under- 

 lying pigment. 



Another species of Callibcet/'s (probably californica) was 

 studied in connection with hageni. The latter is the larger of 

 the 2 species but the eye structure of the male of this smaller 

 form differs from that just described for hageni in but two par- 

 ticulars that are worth attention : 



Proc. Wash. Acad. Sci., March, 1907. 



