226 



Journal of Comparative Neurology. 



come to lie at different levels and many of the cells become 

 spindle shaped. Every cell, however, extends to the cavity of 

 the cup and ends in a rod or fiber probably homologous with 

 the cilia of the epithelium (Fig. 2, P). The cup of each of 

 eye is filled with a homogeneous substance probably a secre- 

 tion of its cells and into this lens the rods from the cells project. 

 While Schewiakoff (Morph. Jahrb., Bd. XV, H. i.) main- 

 tains the existence of two kinds of retinal cells (pigmented, 

 supporting cells, and spindle shaped, or visual cells) for these 

 eyes, as well as for the complex eyes, to be distinguished prin- 

 cipally by their pigmentation and location of nuclei, neither Co- 

 nant nor myself have been able to demonstrate any such two 

 kinds of cells for the simple eyes. 



The larger complex eye is the more complicated of the 

 complex eyes and consists of the following parts: a cellular 



cornea continuous with the sur- 

 face epithelium, a cellular lens, 

 a homogeneous capsule to the 

 lens, a vitreous body composed 

 of prismatic elements, and a 

 retina of pigmented cells whose 

 central processes pass into the 

 nerve tissue lying centrally from 

 the retina. Figs, i, 4, 5. 



The points in Schewiakoff's 

 paper which neither Conant nor 

 myself could verify relate to the 

 structure of the retina and the 

 vitreous body and these will 

 here be specially considered. I, 

 myself, believe I can readily 

 demonstrate two kinds of cells 

 in the retina of the larger com- 

 plex eye, but not on grounds of 

 pigmentation and position of nuclei as Schewiakoff maintained, 

 but from four reasons: ist, the pigment of the one kind, the 

 long pigment cells (to retain Conant's nomenclature), may be 



V NT 



Explanation to J^ig. j. This 

 figure shows only a small portion of 

 a retina with its underlying nerve 

 tissue. It shows the central processes 

 of the long pigment cells nicely and 

 seems to show the cells themselves in 

 a retracted condition. This retina 

 was killed in the diirk but contained 

 little pigment. LP — long pigment 

 cell ; SP — short pigment cell ; NT — 

 nerve tissue ; V — vacuole. 



