4. CHEMORECEPTION
91
Fig. 5. Diagrammatic illustration of the essential difference in glomerular transmission between fishes ( a ) and mammals ( b ) : Com. ant., anterior commissure; and
Tr. olf., olfactory tract. From Allison (1953).
The morphology of the brain has been related to the ecological habits
of fishes ( Uchihashi, 1953; Schnitzlein, 1964). According to the morphological development of the brain, fishes may be classified as forebrain-,
mesencephalon-, or medulla oblongata-developed groups. Those species
in which the forebrain is well developed (Anguilla) have also a large
medulla oblongata and are usually nocturnal; this indicates a dominance
of olfactory and gustatory functions. Species in which the facial and vagal
lobes are conspicuously developed (catfish and carp) show gustatory
feeding behavior.
111. BEHAVIORAL STUDIES OF CHEMORECEPTIVE FUNCTIONS
A. Olfactory Sense
Accurate learning experiments in fish were first made by Strieck
( 1924). Minnows, Phoxinus phorinus, were trained to discriminate' pure
odorous (coumarin, skatol, and muscone) and gustatory (glucose, acetic
acid, and quinine) substances. These substances were readily detected by
minnows. However, trained fishes were unable to discriminate odorous
substances after the forebrain was removed although they could still
91
Fig. 5. Diagrammatic illustration of the essential difference in glomerular transmission between fishes ( a ) and mammals ( b ) : Com. ant., anterior commissure; and
Tr. olf., olfactory tract. From Allison (1953).
The morphology of the brain has been related to the ecological habits
of fishes ( Uchihashi, 1953; Schnitzlein, 1964). According to the morphological development of the brain, fishes may be classified as forebrain-,
mesencephalon-, or medulla oblongata-developed groups. Those species
in which the forebrain is well developed (Anguilla) have also a large
medulla oblongata and are usually nocturnal; this indicates a dominance
of olfactory and gustatory functions. Species in which the facial and vagal
lobes are conspicuously developed (catfish and carp) show gustatory
feeding behavior.
111. BEHAVIORAL STUDIES OF CHEMORECEPTIVE FUNCTIONS
A. Olfactory Sense
Accurate learning experiments in fish were first made by Strieck
( 1924). Minnows, Phoxinus phorinus, were trained to discriminate' pure
odorous (coumarin, skatol, and muscone) and gustatory (glucose, acetic
acid, and quinine) substances. These substances were readily detected by
minnows. However, trained fishes were unable to discriminate odorous
substances after the forebrain was removed although they could still