62 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 
certain places. Yet, the fact that the cells of the proximal walls 
of the distal eyes have their pigmented portions nearly double the 
usual length, shows some deeper significance. 
I also note here the small secondary, non-pigmented invagination 
into the tissue of the clubs from each of the distal simple eyes. 
Schewiakoff describes this invagination, and it extends in a proximal 
and dorsal direction (dorsal-side of club opposite complex eye) from 
the dorsal sides of the distal simple eyes. The cells of these 
invaginations are not pigmented, but quite like the other pigmented 
cells in shape, and like these with distal flagellate fibers. I do not 
see the necessity of assuming, however, that these secondary invagi- 
nations are the real sensitive parts of these eyes, while the pigmented 
parts serve as an iris, as Schewiakoff does in his general discussion. 
The histological structure of both pairs of simple eyes is the 
same. Sections and macerations give me evidence of only one kind 
of cells, all pigmented alike (except, of course, the non-pigmented 
secondary invaginations just noted). The cells in these eyes are 
very closely crowded so that their nuclei lie at several different 
levels. That they all extend to the lumen of the eyes and are all 
pigmented could be demonstrated with certainty in many sections, 
when some of these cells whose nuclei lay most centrad could be 
followed with the greatest nicety to the lumen (Fig. 12). Macerations 
(Figs. 8, unlettered cells 21) also show cells with very long cell bodies 
pigmented at their distal ends and occasionally with a distal process 
or fiber. While there are, therefore, spindle-shaped cells found, yet 
they are in every other respect alike, and their differences of shape 
and position of nuclei are simply the result of crowding. ‘There is, 
therefore, no evidence of supporting (pigmented) cells and spindle- 
shaped visual cells (pigmented only externally) as Claus and 
Schewiakoff have described and which Conant and myself cannot 
corroborate. 
Distally, the retinal cells of the simple eyes have each a fiber 
(flagellum) that extends into the lumen (Figs. 12, 15, 16, 21). Hach 
flagellum has a dumbbell-shaped basal body just on its entrance into 
its cell quite like the basal bodies described for the visual cells of 
the complex eyes (Fig. 12, part left unpigmented). Each flagellum, 
or fiber, can usually be seen to extend into the cell. In one series I 
found appearances like Fig. 16, which is a drawing of a part of a 
section through one of the proximal simple eyes. This section is 
