78
J. N. BALL AND BRIDGET I. BAKER
ventral and dorsal zones and showed that the activity was stronger in the
ventral zone; the basophils of these two zones displayed secretory changes
correlated with gonadal development ( Barannikova, 1949, 1954 ) , identifying these cells as gonadotrops. The gonadotrops display marked development of acidophilic granules during their activity cycle, reminiscent
of the R granules of Poecilia and other teleosts ( Section 11, B, 4 ) .
Since the gonadotrops are associated in both dorsal and ventral zones
with a weakly staining acidophil, apparently distinct from the rostral
acidophils, we may provisionally conclude that these two zones in A. stellatus correspond to the teleostean proximal pars distalis. However, as in
holosteans, there is no very sharp separation of the two regions of the
pars distalis, with broad mixed zones exhibiting all the cell types (Kerr,
1949).
The pars intermedia is very large, and consists almost entirely of large
basophils together with small numbers of chromophobes and acidophils
( Kerr, 1949). The neurohypophysis is separated from the adenohypophysis by a connective tissue layer, except in places over the pars intermedia
where long hollow neurohypophysial processes penetrate deeply among
the endocrine cells, with ependymal cells lining the cavities of the processes in the usual arrangement. No processes penetrate the pars distalis
( Kerr, 1949). Neurosecretory axons from the NPO and possibly also from
the NLT terminate on blood vessels in the neurohypophysial processes
( Sathyanesan and Chavin, 1967). The connective tissue sheet between
the infundibular floor (anterior neurohypophysis) and pars distalis is
vascularized, and as in holosteans neurosecretory fibers from the NPO
may terminate in relation to these capillaries, forming a kind of median
eminence ( Sathyanesan and Chavin, 1967; Kerr, 1968; Polenov, 1966).
B. Superorder Holostei ( Amia and Lepisosteus)
An account of the anatomy and histology of the pituitary in both
genera is available (Kerr, 1949), and one of us (Ball, 1968) has investigated the glands of 4 Amia and 3 Lepisosteus using the modern
techniques discussed in Section I, B.
Neither genus preserves a hypophysial cavity or duct in the adult.
The gland lies attached along most of its length to the infundibular floor
(anterior neurohypophysis) and in Amia is relatively shorter and deeper
than in Lepisosteus. Behind the pituitary is a large saccus vasculosus
( Section 11, E ) . Both genera display to a marked degree an intermingling
of all the cell types in the pars distalis, as in the sturgeons, so that it is
difficult to divide the area clearly into rostral and proximal regions.
J. N. BALL AND BRIDGET I. BAKER
ventral and dorsal zones and showed that the activity was stronger in the
ventral zone; the basophils of these two zones displayed secretory changes
correlated with gonadal development ( Barannikova, 1949, 1954 ) , identifying these cells as gonadotrops. The gonadotrops display marked development of acidophilic granules during their activity cycle, reminiscent
of the R granules of Poecilia and other teleosts ( Section 11, B, 4 ) .
Since the gonadotrops are associated in both dorsal and ventral zones
with a weakly staining acidophil, apparently distinct from the rostral
acidophils, we may provisionally conclude that these two zones in A. stellatus correspond to the teleostean proximal pars distalis. However, as in
holosteans, there is no very sharp separation of the two regions of the
pars distalis, with broad mixed zones exhibiting all the cell types (Kerr,
1949).
The pars intermedia is very large, and consists almost entirely of large
basophils together with small numbers of chromophobes and acidophils
( Kerr, 1949). The neurohypophysis is separated from the adenohypophysis by a connective tissue layer, except in places over the pars intermedia
where long hollow neurohypophysial processes penetrate deeply among
the endocrine cells, with ependymal cells lining the cavities of the processes in the usual arrangement. No processes penetrate the pars distalis
( Kerr, 1949). Neurosecretory axons from the NPO and possibly also from
the NLT terminate on blood vessels in the neurohypophysial processes
( Sathyanesan and Chavin, 1967). The connective tissue sheet between
the infundibular floor (anterior neurohypophysis) and pars distalis is
vascularized, and as in holosteans neurosecretory fibers from the NPO
may terminate in relation to these capillaries, forming a kind of median
eminence ( Sathyanesan and Chavin, 1967; Kerr, 1968; Polenov, 1966).
B. Superorder Holostei ( Amia and Lepisosteus)
An account of the anatomy and histology of the pituitary in both
genera is available (Kerr, 1949), and one of us (Ball, 1968) has investigated the glands of 4 Amia and 3 Lepisosteus using the modern
techniques discussed in Section I, B.
Neither genus preserves a hypophysial cavity or duct in the adult.
The gland lies attached along most of its length to the infundibular floor
(anterior neurohypophysis) and in Amia is relatively shorter and deeper
than in Lepisosteus. Behind the pituitary is a large saccus vasculosus
( Section 11, E ) . Both genera display to a marked degree an intermingling
of all the cell types in the pars distalis, as in the sturgeons, so that it is
difficult to divide the area clearly into rostral and proximal regions.