62 JOHNS HOPKINS UNIVEESITY MOEPHOLOGICAL MONOGKAPHS. 



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 Glaus 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). Each 

 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 



