gland does not open into the branchial entrance but into the peribranchial chamber, but these are usually secondary openings and a
primary opening in the brtinchial region still exists. Godeaux (1957)
reported that in small aplousobranch ascidians of the family Polyclinidae ( - Synoicidae) the neural gland picked up from the water
stream and phugocytoved particles of less than 1 p diameter, but it is
not clear what function this might serve. However, this is the size
range of ascidian spermatozoa and Godeaux’s observations may in fact
lend support to Carlisle’s ( 1 951) theory that the gland detects gametes
in the water.
(c) #ensor!/ structure. Hancock ( 1868) first suggested a special sensory
function for the dorsal tubercle, and assumed that it might act to test
the incoming water current. Although Hunter (1 898) claimed to have
found sensory cells amongst the ciliated cells on the funnel, later authors
have not found any innervation of this region which would suggest a
sensory function (Millar, 1953a). Carlisle (I 95Ob) suggested that in the
pelagic tunicate Salpa the ciliated pit might act as a receptor organ for
judging the density of particles in the inhalant water current. In later
papers (Carlide, 1951, 1953) concerning the whole neural gland he
suggests a special sensory function in connection with the detection of
gametes in the water; thc pathways in this postulated mechanism
would be chemical and not nervous.
As well as suggesting a mucus
secreting role for the gland R80ule also believed that it might act as a
form of digestive glrmd. Butcher (1 930) tested extracts of the gland
for amylase, lipase and protease and concluded that none of these
enzymes is present. Apparently no one has considered this possibility
since that time and yet it merits further attention particularly in the
light of Lane’s (3971) sugge~tion that distension of the rough endoplnsmic reticulum in the compact phase of the gland may indicate
active protein synthesis and the production of hydrolytic enzymes.
There is unequivocal evidence that the neural gland undergoes cyclical
changes in which a cellular discharge accumulates in the lumen. If
PBrhs and Millar are correct in stating that the principal ciliary currents
beat out of the gland then some of this material must be being discharged through the ciliated funnel. The ciliated funnel is located at
the junction of the two peripharyngeal bands and the dorsal lamina
(Fig. 29). It is thus ideally situated for discharging material in a position to bc wrapped u p in the developing food cord ; in many ascidians
the anterior end of thcb laminn forms u folded gutter which leads back
from the ciliated funnel. Finally it seems significant that the degree of
developmerit of the dorsal tubercle, on which opens the ciliated funnel,
(d) Digestive gEand (Rode, 1884).
primary opening in the brtinchial region still exists. Godeaux (1957)
reported that in small aplousobranch ascidians of the family Polyclinidae ( - Synoicidae) the neural gland picked up from the water
stream and phugocytoved particles of less than 1 p diameter, but it is
not clear what function this might serve. However, this is the size
range of ascidian spermatozoa and Godeaux’s observations may in fact
lend support to Carlisle’s ( 1 951) theory that the gland detects gametes
in the water.
(c) #ensor!/ structure. Hancock ( 1868) first suggested a special sensory
function for the dorsal tubercle, and assumed that it might act to test
the incoming water current. Although Hunter (1 898) claimed to have
found sensory cells amongst the ciliated cells on the funnel, later authors
have not found any innervation of this region which would suggest a
sensory function (Millar, 1953a). Carlisle (I 95Ob) suggested that in the
pelagic tunicate Salpa the ciliated pit might act as a receptor organ for
judging the density of particles in the inhalant water current. In later
papers (Carlide, 1951, 1953) concerning the whole neural gland he
suggests a special sensory function in connection with the detection of
gametes in the water; thc pathways in this postulated mechanism
would be chemical and not nervous.
As well as suggesting a mucus
secreting role for the gland R80ule also believed that it might act as a
form of digestive glrmd. Butcher (1 930) tested extracts of the gland
for amylase, lipase and protease and concluded that none of these
enzymes is present. Apparently no one has considered this possibility
since that time and yet it merits further attention particularly in the
light of Lane’s (3971) sugge~tion that distension of the rough endoplnsmic reticulum in the compact phase of the gland may indicate
active protein synthesis and the production of hydrolytic enzymes.
There is unequivocal evidence that the neural gland undergoes cyclical
changes in which a cellular discharge accumulates in the lumen. If
PBrhs and Millar are correct in stating that the principal ciliary currents
beat out of the gland then some of this material must be being discharged through the ciliated funnel. The ciliated funnel is located at
the junction of the two peripharyngeal bands and the dorsal lamina
(Fig. 29). It is thus ideally situated for discharging material in a position to bc wrapped u p in the developing food cord ; in many ascidians
the anterior end of thcb laminn forms u folded gutter which leads back
from the ciliated funnel. Finally it seems significant that the degree of
developmerit of the dorsal tubercle, on which opens the ciliated funnel,
(d) Digestive gEand (Rode, 1884).