158
A. M. PERKS
tory activity of the hypothalamus ( Phoxinus laevis, Fundulus heteroclitzrs,
Scharrer, 1928, 1930, 1932). Its cells are loosely packed in Anguilla anguilla, occur in small clusters in Carmsius auratus, but form larger groups
in Gadus mmrhua, Cottus bubalis, and Salmo irideus (Leatherland et al.,
1966; Palay, 1960; Lederis, 1962). Their shape has been described by a
variety of terms-flask-shaped in Carassius auratus, fusiform or round
in Porichthys notatus, and polygonal in Platypoecilus maculattcs (Palay,
1960; Sathyanesan, 1965b; Oztan, 1963). However, Stutinsky ( 1953) has
pointed out that in Anguilla vulgaris, the cells close to the ependyma are
bipolar while the majority of cells, which lie deeper, are rounded, polyhedral, and multipolar.
The nuclei of the preoptic cells contain a well-marked, rounded
nucleolus ( sazan, carp; Polenov, 1960). These nuclei are eccentrically
placed in the cells, and although sometimes round or oval in shape, they
become irregular and folded in appearance, owing to deep invaginations
of the cytoplasm, which may even include secretory granules (Carassizrs
auratus, Palay, 1960; carp, sazan, Polenov 1960; Salmo irideus, Follenius,
1963; Porichthys notatus, Sathyanesan, 1965b). It is possible that extreme
indentation of this type could account for the multinucleated cells seen in
Anguilla vulgaris by Stutinsky (1953), and in the carp and sazan by
Polenov ( 1960). Enami ( 1955) has observed similar indentations in
Anguilla japonica, and in addition he has described a remarkable transformation of whole cellular nuclei into structureless, Gomori-negative
colloid. This fundamental change has not been reported by any other
workers. However, Oztan (1963) (Platypoecilus muculatus) has seen
differences in nuclear structure which may have reflected different states
in the activity of the preoptic cells, and Polenov ( 1960) (carp, sazan) has
observed apparently pycnotic nuclei in cells which were densely loaded
with neurosecretion.
Outside the nucleus, the cytoplasm of the neurosecretory cells
can be divided into an inner and an outer zone. Usually, the outer,
peripheral zone contains only the membranes and cysternae of the
endoplasmic reticulum ( Nissl substance ) , but electron-lucent vesicles
have been seen in the eel, Anguilla (Salmo irideus, Perca fluuiatilis, Follenius, 1962, 1963; Lederis, 1962; Carassius auratus, Palay, 1960; carp
and sazan, Polenov, 1960; Mugil cephalus, Leray and Stahl, 1961; Gadus
morrhua, Cottus bubalis, Lederis 1962; Anguilla anguilla, Leatherland
and Dodd, 1969a). In contrast, the inner, central zone contains many inclusions, some of which do not fall into any ready classification (Opsanus
tau, Scharrer, 1962). Nevertheless, rod-shaped mitochondria have been
seen in many species, for example, in Gadus morrhua (Lederis, 1962).
Large, round vacuoles, or smooth surfaced vesicles with electron-lucent
A. M. PERKS
tory activity of the hypothalamus ( Phoxinus laevis, Fundulus heteroclitzrs,
Scharrer, 1928, 1930, 1932). Its cells are loosely packed in Anguilla anguilla, occur in small clusters in Carmsius auratus, but form larger groups
in Gadus mmrhua, Cottus bubalis, and Salmo irideus (Leatherland et al.,
1966; Palay, 1960; Lederis, 1962). Their shape has been described by a
variety of terms-flask-shaped in Carassius auratus, fusiform or round
in Porichthys notatus, and polygonal in Platypoecilus maculattcs (Palay,
1960; Sathyanesan, 1965b; Oztan, 1963). However, Stutinsky ( 1953) has
pointed out that in Anguilla vulgaris, the cells close to the ependyma are
bipolar while the majority of cells, which lie deeper, are rounded, polyhedral, and multipolar.
The nuclei of the preoptic cells contain a well-marked, rounded
nucleolus ( sazan, carp; Polenov, 1960). These nuclei are eccentrically
placed in the cells, and although sometimes round or oval in shape, they
become irregular and folded in appearance, owing to deep invaginations
of the cytoplasm, which may even include secretory granules (Carassizrs
auratus, Palay, 1960; carp, sazan, Polenov 1960; Salmo irideus, Follenius,
1963; Porichthys notatus, Sathyanesan, 1965b). It is possible that extreme
indentation of this type could account for the multinucleated cells seen in
Anguilla vulgaris by Stutinsky (1953), and in the carp and sazan by
Polenov ( 1960). Enami ( 1955) has observed similar indentations in
Anguilla japonica, and in addition he has described a remarkable transformation of whole cellular nuclei into structureless, Gomori-negative
colloid. This fundamental change has not been reported by any other
workers. However, Oztan (1963) (Platypoecilus muculatus) has seen
differences in nuclear structure which may have reflected different states
in the activity of the preoptic cells, and Polenov ( 1960) (carp, sazan) has
observed apparently pycnotic nuclei in cells which were densely loaded
with neurosecretion.
Outside the nucleus, the cytoplasm of the neurosecretory cells
can be divided into an inner and an outer zone. Usually, the outer,
peripheral zone contains only the membranes and cysternae of the
endoplasmic reticulum ( Nissl substance ) , but electron-lucent vesicles
have been seen in the eel, Anguilla (Salmo irideus, Perca fluuiatilis, Follenius, 1962, 1963; Lederis, 1962; Carassius auratus, Palay, 1960; carp
and sazan, Polenov, 1960; Mugil cephalus, Leray and Stahl, 1961; Gadus
morrhua, Cottus bubalis, Lederis 1962; Anguilla anguilla, Leatherland
and Dodd, 1969a). In contrast, the inner, central zone contains many inclusions, some of which do not fall into any ready classification (Opsanus
tau, Scharrer, 1962). Nevertheless, rod-shaped mitochondria have been
seen in many species, for example, in Gadus morrhua (Lederis, 1962).
Large, round vacuoles, or smooth surfaced vesicles with electron-lucent