126
A. M. PERKS
111. CARTILAGINOUS FISH: THE ELASMOBRANCHS
A. The Structure of the Neurohypophysis of the Elasmobranchs
The pituitary of the elasmobranchs appears to be markedly different
from that of the cyclostomes, and it is undoubtedly more advanced. However, there are a few surprising aspects which are reminiscent of both the
hagfishes and the lampreys.
As early as 1685, Collins had illustrated the pituitary of the “skait”
( Fig. 3) ; he wrote, “The lower region of the brain of a skait seemeth to
be composed of three ranks of processes, and an odd one.” The “odd one”
was an unusually large, spherical, centrally located process which lay
beneath the caudal extremity of the saccus vasculosus; it was clearly
the neurointermediate lobe of the pituitary. Despite this early start, evidence for the existence of a neurohypophysis in the elasmobranchs was
slow to take shape. Many early workers failed to find any area which
could be termed a pars nervosa (Gentes, 1907; Herring, 1913, 1914). A
few investigators accepted the thin infundibular lamina of the ventral
surface of the brain as the only possible candidate for the neural lobe
( Stendell, 1913; Charipper, 1937). However, in 1926 both Pokorny and
de Beer observed areas of neuroglia-type cells within the pars intennedia
of Raiu clavata and other species, and this was confirmed by Howes in
1936. The reason for the early difficulties became clear when Scharrer
( 1952) used Gomori’s chrome-hematoxylin-phloxin technique to demonstrate the presence of a complete neurohypophysial system in Scyliorhinus
stellar6 (syn. Scyllium stellare). He showed that the pars nervosa was a
diffuse structure which penetrated throughout the tissue of the pars intermedia. Soon afterward, these observations were extended to Raia clauata,
Dasyatis marinus, Torpedo ocelluta, and Scyliorhinus caniculus ( Bargmann, 1955). At about the same time, van der Kamer and Verhagen
(1954, 1955) gave a detailed description of the histology of the pars
nervosa of Scyliorhinus caniculus. They observed the presence of both
pituicytes, and of secretory “parenchymatous pituicytes,” which they
considered to be possible sources of hormones. In 1960, Perks, Dodd, and
Dodd, working on the same species, confirmed the general structure of
the neurohypophysial system by the use of the chrome-hematoxylinphloxin stain, and showed that the neurosecretory droplets were probably
rich in sulfur, since they stained by the performic acid-Alcian blue
method of Adams and Sloper (1956). The vacuolated parenchymatous
pituicytes did not show any evidence for a high sulfur content, and therefore they were unlikely to be a source of neurohypophysial peptides
A. M. PERKS
111. CARTILAGINOUS FISH: THE ELASMOBRANCHS
A. The Structure of the Neurohypophysis of the Elasmobranchs
The pituitary of the elasmobranchs appears to be markedly different
from that of the cyclostomes, and it is undoubtedly more advanced. However, there are a few surprising aspects which are reminiscent of both the
hagfishes and the lampreys.
As early as 1685, Collins had illustrated the pituitary of the “skait”
( Fig. 3) ; he wrote, “The lower region of the brain of a skait seemeth to
be composed of three ranks of processes, and an odd one.” The “odd one”
was an unusually large, spherical, centrally located process which lay
beneath the caudal extremity of the saccus vasculosus; it was clearly
the neurointermediate lobe of the pituitary. Despite this early start, evidence for the existence of a neurohypophysis in the elasmobranchs was
slow to take shape. Many early workers failed to find any area which
could be termed a pars nervosa (Gentes, 1907; Herring, 1913, 1914). A
few investigators accepted the thin infundibular lamina of the ventral
surface of the brain as the only possible candidate for the neural lobe
( Stendell, 1913; Charipper, 1937). However, in 1926 both Pokorny and
de Beer observed areas of neuroglia-type cells within the pars intennedia
of Raiu clavata and other species, and this was confirmed by Howes in
1936. The reason for the early difficulties became clear when Scharrer
( 1952) used Gomori’s chrome-hematoxylin-phloxin technique to demonstrate the presence of a complete neurohypophysial system in Scyliorhinus
stellar6 (syn. Scyllium stellare). He showed that the pars nervosa was a
diffuse structure which penetrated throughout the tissue of the pars intermedia. Soon afterward, these observations were extended to Raia clauata,
Dasyatis marinus, Torpedo ocelluta, and Scyliorhinus caniculus ( Bargmann, 1955). At about the same time, van der Kamer and Verhagen
(1954, 1955) gave a detailed description of the histology of the pars
nervosa of Scyliorhinus caniculus. They observed the presence of both
pituicytes, and of secretory “parenchymatous pituicytes,” which they
considered to be possible sources of hormones. In 1960, Perks, Dodd, and
Dodd, working on the same species, confirmed the general structure of
the neurohypophysial system by the use of the chrome-hematoxylinphloxin stain, and showed that the neurosecretory droplets were probably
rich in sulfur, since they stained by the performic acid-Alcian blue
method of Adams and Sloper (1956). The vacuolated parenchymatous
pituicytes did not show any evidence for a high sulfur content, and therefore they were unlikely to be a source of neurohypophysial peptides