THE EYE OF PECTBN. 81 



delicate lougitndinal fibrilla) in the protoplasm of tlie distal 

 ends of the cells, rnnning to the bases of the processes 

 (PL 7, fig-. 13, D.S.). Like Hesse I have fonnd no motion 

 of the processes in living cells. Between the cells pass 

 branches of the distal nerve, which can be traced quite easily 

 through the septum, but with great difficulty in the i-etina, 

 where it has been uncertain whether they entered into con- 

 nection with the outer cells, interstitial cells, or ended free. 



I think it is certain that they terminate, however, in the 

 distal cell-layer and become connected with the cells, not by 

 the cilia-like processes, but to their sides (PI. 7, fig. 13), It 

 is easy to see in sections the nerve-fibre passing to tlie side or 

 apparently one corner of the distal cell, and in macerations 

 each distal cell can be seen to possess a long, thicker process 

 which appears to arise at the edge of the distal end, but can 

 often be traced some distance down the side wall. This is 

 unfortunately very difficult to make out, but is confirmed, I 

 think, by the character of the distal cells, which are those of 

 sense-cells, and by sections of young eyes, where the inter- 

 stitial cells are only slightly or not at all developed (as 

 noticed by Hesse). 



The nucleus requires special consideration since it differs 

 from that of the interstitial cells. Fig. 16 (PI. 7) illustrates 

 a transverse section through distal and interstitial cells 

 stained with Mallor3^ The nucleus of the first-named 

 (fig. 16, D.S.n.) is large, perfectly round, and contains a 

 number of small chromatin granules, which stain orange red 

 (orange Gr. and saurefuchsin) in addition to the distinct nucle- 

 olus which is always present and stains more distinctly 

 orange (there may be two nucleoli present). The cytoplasm 

 is stained red. These nuclei are very similar in appeai-atice 

 to those of the rod-cells to be considered below and to the 

 nuclei of nerve-cells fi'om the various ganglia. The cliaracter 

 of the outer interstitial cells (fig. 13, O.I.c.) is very 

 different, and I have termed thetn "supporting cells." They 

 bear no resemblance to sense- or nerve-cells, and no connec- 

 tion between them and the inner interstitial cells or the fibres 



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