No. I.] EPITHELIUM OF MUSTELUS CANIS. 75 
be traced into the cells (Figs. 23-25). A careful comparison 
of the size and relative position of these cells with others in the 
same section and in other preparations led to the conclusion 
that this was no exception to the arrangement found in other 
cases, and that there was no evidence of the nerve fiber enter- 
ing the cell. The section cut the hair cells obliquely, the 
proximal end, or base, being higher than the distal end. It is 
almost certain that parts of two or three cells are shown, and 
that the nerve termination is of the same kind as that shown 
in Figs. 14 and 17. 
It is interesting to note that the nerve endings so intimately 
associated with the hair cells are not in any case observed 
placed at a higher level than the nucleus. 
In some poorly stained preparations a granular mass was 
observed at the base of the hair cells, but it was found that the 
granules were observed at different levels in other specimens, 
and were almost entirely lacking in sections that showed the 
nerve fibers most distinctly. 
IV. Conclusions. 
(1) In good preparations there is no trace in Mustelus of 
Kaiser’s cup-like nervous mass at the base of the hair cells. 
(2) The varicosities on the nerve fibers are very rare, and 
when present are caused by the separation of the sheath from 
the nerve fiber. 
(3) The terminal enlargement of the nerve fibre is not like 
the varicosities, as it is always present. 
(4) The triangular enlargements observed at the points where 
the nerves branch are also due to the nerve sheath, through 
which the nerve fibers can be seen. 
(5) When the physiological effect of the methylen blue is 
obtained, the hair cells are not stained. 
(6) The staining of a cell does not necessarily indicate that 
it is a nerve cell. 
(7) When dying tissue is used, cells are frequently deeply 
stained, making it impossible to determine their relation to the 
nerve fibers. 
