164
A. M. PERKS
However, the pars nervosa is often hard to delineate precisely in the
teleosts: Early workers realized that the adult teleost pituitary had no
clearly separate lobes, and that the various regions were fused into a
complex, which, although relatively consistent throughout the group, was
unlike that found in the higher vertebrates (de Beer, 1926; Charipper,
1937; Kerr, 1949). Although there is a clear division between the neural
and the adenohypophysial tissues in juvenile teleosts ( Anguilla anguilla,
Knowles and Vollrath, 1966a; Salmo salar, Klein, 1967), one of the most
notable features of the adult pituitary is the penetration of the neural
component into all parts of the adenohypophysis (Kerr, 1949; Pickford
and Atz, 1957; Legait and Legait, 1957; Leray and Stahl, 1961; Lenys,
1962; Knowles and Vollrath, 1965c; Leatherland et al., 1966; Knowles
et al., 1967). In adult teleosts, the pars nervosa forms digitate processes
which branch and form rootlike structures that penetrate deeply into the
adenohypophysial tissue ( e.g., Anguilla anguilla, Stutinsky, 1953; Jasinski, 1961; Charipper, 1937; Knowles and Vollrath, 1966a: carp and sazan,
Polenov, 1960: PZatypoeciZus muculatus, Oztan, 1963). In the eel,
Anguilla anguilla, the pars nervosa retains primitive characteristics,
for its caudally directed neural processes are penetrated by narrow
canals which extend down from the third ventricle in a situation
reminiscent of the wider canals seen in preteleost groups (Jasinski, 1961;
Dodd and Kerr, 1963; Knowles and Vollrath, 1965a). In a contrasting
situation found in adult specimens of Hilsa ilisha, Sathyanesan (1963)
has described processes of the pars nervosa which pass between adenohypophysial ducts; these unusual ducts connect to a patent oro-hypophysial canal.
In accordance with the early suggestions of Diepen (1954; Esox
lucius), Leray and Stahl (1961) divided the pars nervosa of Mugil
cephalus into two main regions-a rostral region which penetrated the
meso-adenohypophysis, and a caudal region which ramified intimately
into the pars intermedia. The rostral region contained less neurosecretory
material than the caudal division. It passed through the dorsal areas of
the pituitary, close to blood vessels and came into association with acidophyl cells of the meso-adenohypophysis. The situation in Hippocampus
guttulatus was similar, except that the fibers passed to basophylic,
gonadotropic cells present in the same region of this species (Leray and
Stahl, 1961; Da Lage, 1955, 1958). Similar processes, characterized by
the absence or near absence of stainable droplets of neurosecretion, have
been seen in other species such as Gasterosteus aculeatw, Perca fluuiatilis,
Lebistes reticulatus, and Anguilla anguilla (Dodd and Kerr, 1963; Follenius and Porte, 1962; Stutinsky, 1953; see also Bargmann, 1953). Stutinsky (1953) has suggested that in the eel, A. uulgaris, these less heavily
A. M. PERKS
However, the pars nervosa is often hard to delineate precisely in the
teleosts: Early workers realized that the adult teleost pituitary had no
clearly separate lobes, and that the various regions were fused into a
complex, which, although relatively consistent throughout the group, was
unlike that found in the higher vertebrates (de Beer, 1926; Charipper,
1937; Kerr, 1949). Although there is a clear division between the neural
and the adenohypophysial tissues in juvenile teleosts ( Anguilla anguilla,
Knowles and Vollrath, 1966a; Salmo salar, Klein, 1967), one of the most
notable features of the adult pituitary is the penetration of the neural
component into all parts of the adenohypophysis (Kerr, 1949; Pickford
and Atz, 1957; Legait and Legait, 1957; Leray and Stahl, 1961; Lenys,
1962; Knowles and Vollrath, 1965c; Leatherland et al., 1966; Knowles
et al., 1967). In adult teleosts, the pars nervosa forms digitate processes
which branch and form rootlike structures that penetrate deeply into the
adenohypophysial tissue ( e.g., Anguilla anguilla, Stutinsky, 1953; Jasinski, 1961; Charipper, 1937; Knowles and Vollrath, 1966a: carp and sazan,
Polenov, 1960: PZatypoeciZus muculatus, Oztan, 1963). In the eel,
Anguilla anguilla, the pars nervosa retains primitive characteristics,
for its caudally directed neural processes are penetrated by narrow
canals which extend down from the third ventricle in a situation
reminiscent of the wider canals seen in preteleost groups (Jasinski, 1961;
Dodd and Kerr, 1963; Knowles and Vollrath, 1965a). In a contrasting
situation found in adult specimens of Hilsa ilisha, Sathyanesan (1963)
has described processes of the pars nervosa which pass between adenohypophysial ducts; these unusual ducts connect to a patent oro-hypophysial canal.
In accordance with the early suggestions of Diepen (1954; Esox
lucius), Leray and Stahl (1961) divided the pars nervosa of Mugil
cephalus into two main regions-a rostral region which penetrated the
meso-adenohypophysis, and a caudal region which ramified intimately
into the pars intermedia. The rostral region contained less neurosecretory
material than the caudal division. It passed through the dorsal areas of
the pituitary, close to blood vessels and came into association with acidophyl cells of the meso-adenohypophysis. The situation in Hippocampus
guttulatus was similar, except that the fibers passed to basophylic,
gonadotropic cells present in the same region of this species (Leray and
Stahl, 1961; Da Lage, 1955, 1958). Similar processes, characterized by
the absence or near absence of stainable droplets of neurosecretion, have
been seen in other species such as Gasterosteus aculeatw, Perca fluuiatilis,
Lebistes reticulatus, and Anguilla anguilla (Dodd and Kerr, 1963; Follenius and Porte, 1962; Stutinsky, 1953; see also Bargmann, 1953). Stutinsky (1953) has suggested that in the eel, A. uulgaris, these less heavily