104
TOSHIAKI J. HARA
They responded readily to NaCl and KCI solutions (1 M ) . Divalent
cations such as Ca and Mg were inhibitory. Responses to acid, sugar, and
quinine were either slight or inhibitory.
V. BIOLOGICAL ASPECTS OF CHEMORECEPTION
A. Chemical Perception of Foods
There are numerous observations of the searching behavior for foods,
and it has been recognized that all senses (e.g., optic, amustic, and chemical) are involved. Clues which initiate searching behavior depend on
the species, history, and schooling tendencies as well as environmental
conditions; some fishes rely more on chemical senses and others more on
optic or acoustic senses. The importance of chemical senses, especially
sense of smell, has been demonstrated in the following observations.
Parker (1910) placed five normal catfish, Ameiurtu, in an aquarium
in which were hung two wads of cheesecloth, one of which contained
minced earthworm. The wad containing the worms was seized and
tugged eleven times by the fishes, while the wad without worms failed
to excite any noticeable reaction in the course of an hour. Fishes whose
barbels were removed but had normal olfactory organs reacted in the
same manner as intact fish; fishes with cut olfactory tracts never seized
the wad containing worms. These findings indicate that the olfactory apparatus of the catfish is useful in sensing food at a distance; catfish truly
scent their foods. Barbels are also very valuable to Ameiurus in procuring
foods only by coming into direct contact with it (Olmsted, 1918). The
eyes of the killifish, FunduZus heteroclitus, in strong contrast with the
catfish, play an important role in the initial stages of procuring food but
actual swallowing of the food depends on other sense, probably olfactory.
Fishes whose olfactory tracts were cut or whose anterior olfactory apertures were stitched never discriminated between two packets of clothone with dogfish meat hidden in it and the other without the food
(Parker, 1911).
The importance of sense of smell in finding foods has long been demonstrated in Selachians. Dogfish, Mustelus canis, failed to recognize and
determine the location of food substances such as crab meat when the
olfactory capsules were occluded with cotton. Food recognition was regained when the cottom was removed; plugging of one nostril did not
seriously affect that ability ( Sheldon, 1911 ). A similar directive influence
of the sense of smell in the dogfish was observed by Parker ( 1914). Normal dogfish found the foods by making combined right- and left-handed
TOSHIAKI J. HARA
They responded readily to NaCl and KCI solutions (1 M ) . Divalent
cations such as Ca and Mg were inhibitory. Responses to acid, sugar, and
quinine were either slight or inhibitory.
V. BIOLOGICAL ASPECTS OF CHEMORECEPTION
A. Chemical Perception of Foods
There are numerous observations of the searching behavior for foods,
and it has been recognized that all senses (e.g., optic, amustic, and chemical) are involved. Clues which initiate searching behavior depend on
the species, history, and schooling tendencies as well as environmental
conditions; some fishes rely more on chemical senses and others more on
optic or acoustic senses. The importance of chemical senses, especially
sense of smell, has been demonstrated in the following observations.
Parker (1910) placed five normal catfish, Ameiurtu, in an aquarium
in which were hung two wads of cheesecloth, one of which contained
minced earthworm. The wad containing the worms was seized and
tugged eleven times by the fishes, while the wad without worms failed
to excite any noticeable reaction in the course of an hour. Fishes whose
barbels were removed but had normal olfactory organs reacted in the
same manner as intact fish; fishes with cut olfactory tracts never seized
the wad containing worms. These findings indicate that the olfactory apparatus of the catfish is useful in sensing food at a distance; catfish truly
scent their foods. Barbels are also very valuable to Ameiurus in procuring
foods only by coming into direct contact with it (Olmsted, 1918). The
eyes of the killifish, FunduZus heteroclitus, in strong contrast with the
catfish, play an important role in the initial stages of procuring food but
actual swallowing of the food depends on other sense, probably olfactory.
Fishes whose olfactory tracts were cut or whose anterior olfactory apertures were stitched never discriminated between two packets of clothone with dogfish meat hidden in it and the other without the food
(Parker, 1911).
The importance of sense of smell in finding foods has long been demonstrated in Selachians. Dogfish, Mustelus canis, failed to recognize and
determine the location of food substances such as crab meat when the
olfactory capsules were occluded with cotton. Food recognition was regained when the cottom was removed; plugging of one nostril did not
seriously affect that ability ( Sheldon, 1911 ). A similar directive influence
of the sense of smell in the dogfish was observed by Parker ( 1914). Normal dogfish found the foods by making combined right- and left-handed