THE ORGAN AND SENSE OF TASTE IN FISHES. 
267 
means, while fishes which lack these organs in the skin have the sense of taste 
confined to the mouth. The delicacy of the sense of taste in the skin is directly 
proportional to the number of terminal buds in the areas in question. 
Numerous unrelated types of bony fishes from the siluroids to the gadoids which 
possess terminal buds have developed specially modified organs to carry the buds and 
increase their efficiency. These organs may take the form of barblets or of free 
filiform fin rays. The free rays of the pelvic and dorsal fins of gadoid fishes are thus 
explained, and indeed this is possibly the motive for the migration into the jugular 
position of the pelvic fins of the gadoids. 
In all cases where terminal buds are found on barblets or filiform fin rays gusta- 
tory nerves belonging to the communis system are distributed to them. These 
barblets and free fin rays likewise receive a very rich innervation of tactile or gen- 
eral cutaneous nerves, so that they merit their popular designation — “feelers." 
Both sets of end organs undoubtedly cooperate in the discrimination of food, and the 
animal has the power of very accurate localization of the stimulus. Whether the 
gustatory stimulus alone can be localized apart from its tactile accompaniment can 
not at present be stated. A purely tactile stimulus with no gustatory element can 
be localized precisely, and I have as yet no conclusive evidence that a pure gustatory 
stimulus, even when strong, can be located by the fish. It is certain that feeble and 
widely diffused gustatory stimuli can not be accurately located by the fishes which I 
have experimented with, either by the terminal buds or by any other organs. 
The fishes in which the cutaneous terminal buds are most highly developed are 
in general bottom feeders of rather sluggish habit, and in some cases they are noc- 
turnal feeders. The high development of this sense is compensated for in some 
fishes by the reduction of others. The visual power of the fishes is especially apt to 
suffer degradation. This degradation may be organic, a positive degeneration of the 
visual apparatus, as in Ameiurus , or it may be merely functional. In the latter 
case, though the organs of vision are not necessarily modified, these organs are not 
actually used in procuring food, the fish being unable to effect visual reflexes toward 
food substances or to correlate visual stimuli with the movements necessary to react 
toward food substances. The fish may be perfectly able to effect other visual 
reflexes, but is apparently unable to understand the significance of food when per- 
ceived by the sense of sight only. This particular central reflex path has never been 
developed, or has atrophied from disuse. Nature has here effected for the species 
something similar to what is accomplished in individual men occasionally by disease, 
in the production of certain aphasias. 
The number of reflex activities habitual to an animal with a nervous system as 
simply organized as the bony fish is probably far smaller than is commonly supposed, 
and these activities are in general characterized by but little complexity of organiza- 
tion. It is probably quite within the range of possibility to determine by observa- 
tion and experiment for any given species of fish, to a high degree of accuracy, what 
these habitual activities are and to work out by histological methods the reflex arc 
within the nervous system for each of them; and since the human nervous system is 
built up on the same general plan as the piscine nervous system it follows that such 
a thorough and systematic correlation of function with structure would be profitable 
from many points of view. 
