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WM. A. KEPNER AND W. H. TALIAFERRO 



this cell presents three regions — lateral, middle, and mesial. 

 The lateral region is a finely granular cone which lies closely 

 applied to the dorsal surface of the ganglion (fig. 8, C). The 

 lateral end of this cone, we infer, is continued as a nerve fiber 

 into the ganglion. The basal or mesial fourth of this cytoplasmic 

 region accommodates the nucleus. The middle cytoplasmic 

 region of the retinular cell is the densest portion of this visual 

 element (fig. 8, L). It is a concavo-convex disc. In a living 

 specimen under a water immersion lens, a highly refractive body 

 is seen at the margin of the pigmented cups of the accessory 



Text fig. C Reconstructed drawing of central nervous system and organs 

 of special sense. Lateral aspect. C, dorsal commissure; DG, dorsal ganglion; 

 E, eye; P, pharynx; NPh, pharyngeal sheath nerve; XCP, ciliated pit nerve; 

 CP, ciliated pit. 



cell; this we regard as this middle curved or lens-shaped part 

 of the C3^toplasm. This region is clearly shown in an axial sec- 

 tion of the fixed cell (fig. 8, L). It is here seen, also to be the 

 densest portion of the cytoplasm and to have the contour of a 

 concavo-convex lens. This lens-shaped cytoplasmic region is so 

 disposed that, if it is functional as a lens, it would cause the rays 

 of light to converge as they pass through the rhabdome to fall 

 upon the pigment of the accessory cell. However, we are not 

 prepared to say that this region does act as such a lens but are 

 content to look upon it as a supporting structure of the mesial 

 cytoplasmic region, which is the rhabdome of the visual cell. 



