No. 4.] 



AMPULLAE OF THE SELACHII. 



173 



ampullary pockets, the nuclei of the thin lining layer of 



the pockets are clearly seen on deep focusing; at a higher 



focus the outlines of the cells and nuclei of the deeper layer 



appear ; at a still higher 



focus the nerve fibrils are 



sharply differentiated 



(Fig. 7). Since these - ,/ , 



/'Hv 



' ' r T^i-n - ./ i i i *fT."?w- 1 / / t . 



&C 



nerve fibrils appear at 

 neither of the two first- 

 mentioned optical levels 

 the observations made 

 from sections of the am- 

 pullary walls appear to be 

 confirmed, namely, that 

 the nerve fibrils ramify 



Only Over the bases Of the FIG. S. Longitudinal section of wall of ampullary 

 Cells Of the deeper laVCr pocket: con. /is., connective tissue; d.c., deeper layer 



of cells ; n.ax.cyl., axis cylinder of nerve ; n.k., nerve 



In frozen Sections pre- knob ; p.c., peripheral layer of cells, x ^ oil immers. 

 i -i ., n , 2 in. occular. 



pared as described above, 



the cells may be isolated from one another by tapping the 

 cover glass. I have seen in several cases a fine, deep-blue 

 fibril running along the surface of the deeper cells and ending 



>*<* 



FIG. Q. Nerve fibrils running over the surface of the deeper layer of cells to end in knobs on the 

 outside: d.c., deeper layer of cells; n.ax.cyl., axis cylinder of nerve ; n.k., nerve knob; p.c., 

 peripheral cell, x pj oil immers. 2 in. occular. 



in a slight enlargement (Fig. 9, n.k.}. These fibers and end- 

 ings are always outside the cells, and it is apparent that the 

 protoplasm of the two structures is not in continuity, since the 

 cells are usually of a yellow color, while the nerve fibrillae are 



