388 J. M. D. OLMSTED 
When first observed they were always hooked over in the form 
of the letter ‘J,’ but after they had reached a length of 5 mm. 
they became straightened. The smaller of the regenerated bar- 
bels were colorless and quite transparent, and histological prepa- 
rations of them showed that they had no chromatophores. By 
the time the regenerated dorsal barbels had reached a length 
of 5 mm. they had become black, and the lateral and ventral 
ones were dead white, the condition characteristic of the ventral 
surface of the fish. In the longer of the regenerated barbels 
taste bud were fully formed, although other structures char- 
acteristic of a mature barbel were lacking. In a eross-section 
was to be seen an outer layer of epidermis in which lay the taste 
buds, but the whole interior was filled with loose mesenchyme 
cells (fig. 24). There was no supporting rod of cartilage, though 
there might be the beginning of it in the condensation of mesen- 
chyme cells near the center, and the nerves were not gathered 
into fascicles. The new barbels were very delicate, and much 
like bits of skin. When the fish was lifted out of the water, 
they lay flat against the surface of the animal and became 
practically invisible. In the water, however, they stood out 
from the head like normal barbels. The longer ones were sensi- 
tive to rods and pieces of worm, the very short ones were not. 
The shorter regenerated barbels showed taste buds in various 
stages of development (fig. 26). The first indication that a 
taste bud was forming was the extension of the dermis up into 
the epidermis to form the characteristic papilla as at a in figure 
26. Capillaries were present, as they are in the mature papilla, 
and after the disappearance of the buds as well. Next occurred 
a proliferation of the cells in the germinative layer at the tip 
of the papilla, so that there were several layers of heavily staining 
nuclei at this point (fig. 26, b). Processes from these cells were 
then sent out toward the surface, and the taste bud was prac- 
tically complete, except that the prolongations of the sense cells 
were very much shorter than in the mature bud (fig. 26, c). In 
fact, the new buds were quite small and lay very close to the 
surface of the epidermis. Nevertheless, they were absolutely 
unmistakable. 
