242 



ADAPTATIONS TO NOCTURNAL ACTIVITY 



Fig. 96 — Retina and tapetum of the rock sturgeon, Acipenser fulvescens. x 500. 



(The large retinal pigment cells each contain pigment. More commonly, in other sturgeons, 

 the cells are small and only a few contain any pigment). 



b,a- bipolar and amacrine cells; c- cone (c/. Fig. 22a, p. 54); cc- choriocapillaris; g- 

 ganglion cells; gm- glass membrane; gt- guanin tapetum, occupying inner portion of 

 chorioid; he- horizontal cells (massive, non-conductive type); pc- pigmented portion of 

 chorioid (largely out of the piaure); pp- pigment-filled process of pigment epithelial 

 cell: T- rod. 



