NERVE CUTTING IN AMIURUS 389 
REGENERATION OF TIPS OF BARBELS WITH AND WITHOUT NERVES 
Upon discovering that the barbel as a whole would regenerate, 
I tried the effect of removing half of this organ to see whether 
regeneration would take place at the injured end. If regeneration 
should occur on the stump of the barbel, as it was reasonable 
to suppose since whole new barbels regenerated when the old 
ones were completely removed, would the cutting of the nerve 
to the barbel have any effect on this regeneration? It was found 
both in the normal barbels and in those with nerves cut that the 
stumps healed over within two days. In the normal barbel 
eight days later a small colorless transparent prolongation could 
be seen extending a millimeter or so beyond the old heavily 
pigmented stump (fig. 15). This new end was of much smaller 
diameter than the old part from which it sprang, so that it 
resembled a small nipple. Histological examination showed that 
the regenerated end was exactly like a regenerating whole barbel 
of the same length. ‘Taste buds did not make their appearance 
until after ten days (fig. 25). But the result on barbels which 
had had their nerves cut was totally different. On seven fish 
in which the nerves to the dorsal and lateral barbels had been 
cut two days before, the tips of each of the dorsal, lateral, and 
ventral barbels had been removed. Ten days later in every one 
of the seven fish regeneration of a nipple-like end had taken place 
in the two ventral barbels only, while in the two dorsal and two 
lateral barbels there was nothing further than a mere healing 
over of the wound (figs. 8, 9). This result was most striking 
on account of the contrast, in the same fish, between the colorless 
or almost white nipple on the stubs of the two normal barbels 
and the smooth rounded black ends of the four barbels with the 
nerves cut. In the latter the epidermis had closed over the 
wound and lay close to the stub of cartilage. This cap of epi- 
dermis possessed no indication of taste buds either old or new. 
The taste buds had disappeared from the whole barbel, since 
it was then twelve days since the nerves had been cut. 
The presence of an intact nerve, therefore, determines not 
only the regeneration of taste buds, but also the regeneration 
of the whole barbel. 
