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the basal end the nucleus causes a rapid increase in the 

 diameter (fig. 30, R. C. n., and fig. 29, B. C. n.). The 

 nuclei of the rod cells are to be found in longitudinal 

 sections through the eye, in a cluster not far from the 

 sides of the retina (fig. 29, E. C. n.) and before the point is 

 reached where the cells curve almost at right angles to 

 form the basal portions, which like a series of columns lie 

 Avith their long axes in a proximal-distal direction. 



Another series of nuclei is generally conspicuous 

 (fig. 30, C. i.), but, as first shown by Patten (35), these do 

 not belong to the rod cells, but belong to cells lying 

 between them (inner interstitial cells). The rod cells all 

 terminate at the same level, or rather pass directly into 

 their continuations — the rods. At the line of junction of 

 these two elements there are traces of a delicate membrane 

 extending across the retina, called by Schreiner (37) the 

 outer sieve membrane (fig. 30, S. m. o.). This is per- 

 forated by the rods, and does not, as Patten stated 

 (terminal membrane), separate the rod cells from the rods, 

 that is, form the actual base of the rod cells. Each rod 

 cell is connected with a rod, the one being a continuation 

 of the other, the line of division being marked by 

 the outer sieve membrane outside the cell, and internally 

 by a difference in cell structure. Like Schreiner, I have 

 seen no vacuole described by Patten as existing at the 

 base of the rod cells. 



The Rods (fig. 30, R.) are difticult to preserve in good 

 condition, but absolute alcohol sublimate gives good 

 results, and sometimes Flemming, though with large 

 Pecten maximus eyes the latter probably does not 

 penetrate quickly enough. They are cone-shaped bodies, 

 longest in the centre of the retina and decreasing slightly 

 in size towards the periphery. The basal portions of the 

 rods are separated from each other by, and rest on, a 



