334 End-Organs of the Trigeminus and Lateralis Nerves 
arates in halves, the cavity of the canal being continuous with the break 
in the ridge. Beneath the canal and ridge is a very decided depression 
of the basement membrane, so that the entire apparatus, canal and ridge 
together, rests in a groove of the dermis (Fig. 10). This groove does 
not terminate with the canal above it, but extends a short distance, some- 
times thirty microns, sometimes one hundred and thirty, beyond it at 
each end. Moreover, where the surface canal is interrupted (Figs. 5 
and 6), sections show the groove beneath to be continuous. 
At one side of the dermal groove in Fig. 7 is seen a second body of 
spindle-shaped cells, inclined towards the canal. These side bundles are 
formed of a row of club-shaped bodies; sometimes they are continuous 
Fic. 9. Cross-section of epidermis of young Bdellostoma, 11 inches long, 
through lateral line canal. Preserved in chromic acid. bB—=basement mem- 
brane, g=—lJateral line canal, m—=mucous cell, N=spindle-cell ridge, t= 
tube beneath canal and above dermal groove. X 333. 
ridges, shorter, however, than the central ridge. Like it they have a defi- 
nite line of cleavage down the center, and are sometimes connected by a 
branch opening directly with the canal. 
Similar club-shaped bundles of spindle cells are also found outside of 
the dermal groove. They are numerous in the territory of the lateralis 
anterior, but much less so in that of the lateralis posterior. Nerve fibers 
run into the bundles, and they are undoubtedly genuine neuromasts. 
In addition to these neuromasts, single sensory cells are found in the 
territory of the dermal groove, (Fig. 10, s). They are larger than the 
epithelial cells about them, are bluntly conical in shape, and do not 
stain readily. These sense cells are not abundant, but a more successful 
method of staining may show them to be more numerous than they 
