108
IVAN (IOODBODT
the close anatomicul i ~ n d ombrayological association between them it
seems reamnable to concludc thnt there may also be a functional
connection.
The neural gland was first described by Hancock (1868) and has
been a subject for study and controversy ever since ; the older literature
has been reviewed by PBr& (1943) and Godeaux (1964a). The gland
consists of a series of folds or evaginations arising from the lower side
of a duct or canal which leads from the dorsal side of the pharynx
inwards toward the nerve ganglion (Fig. 25). The opening of the canal
is usually expanded into a ciliated funnel which is often folded to form
either a simple C-shaped aperture or sometimes a more complex spiral
structure and usually forming a slight projection, the dorsal tubercle.
The dorsal tubercle then repre8ents the ciliated opening of the neural
gland and it is important to recognize its position relevant to other
structures of the branchial sac (Fig. 29). It opens dorsally immediately
anterior to the junction of the peripharyngcal grooves and the dorsal
lamina, and irnmcdiately insidc the branchial siphon posterior to the
branchiul tentaclcs. It i, thus perfectly placed either to “ t e s t ”
material coming in to the branchial sac or to discharge any exocrine
secretion into the beginning of the mucus-wrapped food cord.
According to Godeuux (1964a), PbrBs (1943) and Georges (1971) the
duct from the gland is lined by a cuboidal epithelium which is ciliated
for only a part of its length. This epithelium continues along sides and
top below the nerve ganglion while on the ventral side it proliferates the
glandular epithelium.
It is now generdly agreed that the epithelium of the gland undergoes cyclical changes of activity in which the gland changes from a loose
reticulated form (Fig. 30a) to an expanded compact form (Fig. 306)
resulting from vt~cuolization of the epithelial cells and increased turgor
throughout. Although morphological changes of this sort have been
known for ti long time (Metcalf, 1900; Butcher, 1930) the first comprehensive account is thnt of I’kbs ( I 943). According to this author in the
reticulate phase the lohes of’ the gland awe sufficiently flattened for largo
blood spaccs to cxist hetwc.cn neighbouring lobes but thcsc are Hubstantinlly reduced as the gland becomes turgid PCrb claims that
starting from a simple cuboidal epithelium there is rapid multiplication
of cells which slough off into the lumen of the gland where they assume
a star shape, put out pseudopodia and form a network between the
free cells and those of the intjiict epithelium. Some of thww c d s become
vacuolar i ~ n d
phtlgo:o“.ytin and iwe sugrncnted by blood phagocytes which
penetrate through tlir epithelium to the lumen. Both types of vacuolar
cell phagocytize other cells in the lumen snd as more cells proliferate
IVAN (IOODBODT
the close anatomicul i ~ n d ombrayological association between them it
seems reamnable to concludc thnt there may also be a functional
connection.
The neural gland was first described by Hancock (1868) and has
been a subject for study and controversy ever since ; the older literature
has been reviewed by PBr& (1943) and Godeaux (1964a). The gland
consists of a series of folds or evaginations arising from the lower side
of a duct or canal which leads from the dorsal side of the pharynx
inwards toward the nerve ganglion (Fig. 25). The opening of the canal
is usually expanded into a ciliated funnel which is often folded to form
either a simple C-shaped aperture or sometimes a more complex spiral
structure and usually forming a slight projection, the dorsal tubercle.
The dorsal tubercle then repre8ents the ciliated opening of the neural
gland and it is important to recognize its position relevant to other
structures of the branchial sac (Fig. 29). It opens dorsally immediately
anterior to the junction of the peripharyngcal grooves and the dorsal
lamina, and irnmcdiately insidc the branchial siphon posterior to the
branchiul tentaclcs. It i, thus perfectly placed either to “ t e s t ”
material coming in to the branchial sac or to discharge any exocrine
secretion into the beginning of the mucus-wrapped food cord.
According to Godeuux (1964a), PbrBs (1943) and Georges (1971) the
duct from the gland is lined by a cuboidal epithelium which is ciliated
for only a part of its length. This epithelium continues along sides and
top below the nerve ganglion while on the ventral side it proliferates the
glandular epithelium.
It is now generdly agreed that the epithelium of the gland undergoes cyclical changes of activity in which the gland changes from a loose
reticulated form (Fig. 30a) to an expanded compact form (Fig. 306)
resulting from vt~cuolization of the epithelial cells and increased turgor
throughout. Although morphological changes of this sort have been
known for ti long time (Metcalf, 1900; Butcher, 1930) the first comprehensive account is thnt of I’kbs ( I 943). According to this author in the
reticulate phase the lohes of’ the gland awe sufficiently flattened for largo
blood spaccs to cxist hetwc.cn neighbouring lobes but thcsc are Hubstantinlly reduced as the gland becomes turgid PCrb claims that
starting from a simple cuboidal epithelium there is rapid multiplication
of cells which slough off into the lumen of the gland where they assume
a star shape, put out pseudopodia and form a network between the
free cells and those of the intjiict epithelium. Some of thww c d s become
vacuolar i ~ n d
phtlgo:o“.ytin and iwe sugrncnted by blood phagocytes which
penetrate through tlir epithelium to the lumen. Both types of vacuolar
cell phagocytize other cells in the lumen snd as more cells proliferate