156
9. M. PERKS
the adenohypophysis and that systemic effects might well parallel those
found in the closely related teleosts.
VIII. BONY FISH: THE TELEOSTS
A. The Structure of the Neurohypophysis of the Teleosts
The pioneer work of Scharrer (1928, 1930, 1932), which was carried
out on teleost fish, first showed the presence of neurosecretory cells in the
hypothalamus. After Palay ( 1945) had traced neurosecretory material
throughout the neurohypophysial system of a number of teleost species,
both Bargmann and Scharrer utilized Gomori’s chrome-hematoxylinphloxin stain to demonstrate the presence of a well-developed neurohypophysial system throughout a wide range of teleost fish (Bargmann
and Scharrer, 1951; Bargmann, 1953). Since this time, the teleost pituitary
has been widely studied, partly because of the easy availability of
many species, and partly because of its interesting specializations. Probably the most interesting of these is the remarkable penetration of neurosecretory axons throughout all the regions of the adenohypophysis. This
is not only unique to the teleost fish, but it is also in marked contrast with
the situation in the mammals. Recently, the structure of the teleost neurohypophysis and its relationship to the adenohypophysis has been investigated by means of the electron microscope, and the remarkable studies
of Lederis (1962, 1964), Knowles and Vollrath (1965a,b,c, 1966a,b), and
Leatherland ( 1967 ) have resulted in the teleost neurohypophysis becoming one of the best understood among the lower vertebrates.
Studies of a large number of teleosts have shown that their preoptic
nuclei lie approximately dorsal to the optic chiasma on both sides of the
third ventricle. There are variations in both the position and the length
of the nucleus in different species, with a tendency for it to become located
more rostrally in more advanced species ( Charlton, 1932). In the relatively
primitive eel, Anguillu anguilla, each nucleus consists of a thin sheet of
neurons which extends close beneath the ependyma of the third ventricle,
in the shape of an inverted “ L (Fig. 9) (Stutinsky, 1953; Leatherland
et al., 1966). Charlton’s diagrams (1932) suggest that this pattern is
relatively common, while Oztan’s description (1963) of the preoptic
nucleus of Platypoecilus maculutus as being arc-shaped may indicate
slight variations from this basic theme. The cells of the nucleus are
surrounded or separated by processes from the overlying ependymal cells
(Carassius uuratus; Palay, 1980), and by other structures which include
9. M. PERKS
the adenohypophysis and that systemic effects might well parallel those
found in the closely related teleosts.
VIII. BONY FISH: THE TELEOSTS
A. The Structure of the Neurohypophysis of the Teleosts
The pioneer work of Scharrer (1928, 1930, 1932), which was carried
out on teleost fish, first showed the presence of neurosecretory cells in the
hypothalamus. After Palay ( 1945) had traced neurosecretory material
throughout the neurohypophysial system of a number of teleost species,
both Bargmann and Scharrer utilized Gomori’s chrome-hematoxylinphloxin stain to demonstrate the presence of a well-developed neurohypophysial system throughout a wide range of teleost fish (Bargmann
and Scharrer, 1951; Bargmann, 1953). Since this time, the teleost pituitary
has been widely studied, partly because of the easy availability of
many species, and partly because of its interesting specializations. Probably the most interesting of these is the remarkable penetration of neurosecretory axons throughout all the regions of the adenohypophysis. This
is not only unique to the teleost fish, but it is also in marked contrast with
the situation in the mammals. Recently, the structure of the teleost neurohypophysis and its relationship to the adenohypophysis has been investigated by means of the electron microscope, and the remarkable studies
of Lederis (1962, 1964), Knowles and Vollrath (1965a,b,c, 1966a,b), and
Leatherland ( 1967 ) have resulted in the teleost neurohypophysis becoming one of the best understood among the lower vertebrates.
Studies of a large number of teleosts have shown that their preoptic
nuclei lie approximately dorsal to the optic chiasma on both sides of the
third ventricle. There are variations in both the position and the length
of the nucleus in different species, with a tendency for it to become located
more rostrally in more advanced species ( Charlton, 1932). In the relatively
primitive eel, Anguillu anguilla, each nucleus consists of a thin sheet of
neurons which extends close beneath the ependyma of the third ventricle,
in the shape of an inverted “ L (Fig. 9) (Stutinsky, 1953; Leatherland
et al., 1966). Charlton’s diagrams (1932) suggest that this pattern is
relatively common, while Oztan’s description (1963) of the preoptic
nucleus of Platypoecilus maculutus as being arc-shaped may indicate
slight variations from this basic theme. The cells of the nucleus are
surrounded or separated by processes from the overlying ependymal cells
(Carassius uuratus; Palay, 1980), and by other structures which include