(c) Gmtro-intestinat activihj. Tliere is no tnuscular coating to the
intestinal tract except for it smull sphincter muscle around the anus, and
there is little evidence to xuggt*st that any other part of the canal has a
special innervation.
(d) Gonadin1 activity. Thc gonads might be innervated by neurosecretory fibros and the sphincter rnuscle of the gonoduct may also be
subject to visceral innervation.
(e) Secrcto-motor activity. Various regions of the alimentary system,
and in particular the endostyle, are engaged in mucus secretion some of
which activity might be under viscero-motor control.
Fedele (1923a, 1927) reported the presence of a visceral plexus and
visceral nerve cells in Cionu and in the pelagic tunicate Salpa, but
neither Millar (1953a) nor Boric (1959) were able to find any nerve cells
on the gut of Ciona although Bone did find a few cells on the alimentary
canal of Salpa. In Cionu Bone found some multipolar stellate cells on
the gonoduct which had connwtions to the dorsal nerve but there is
nothing to enablc us to determine the function of these cells. Markman
(1958) was unable to locate any nerve cells outside of the dorsal ganglion
in young Ciona, and found no innervation at all in the intestine.
Innervation of the branchial sac and endostyle has been reported by
aeveral workers. Hunter ( I 898) illustrates nerve fibres from the anterior
region of the ganglion innervating tho endostyle and the branchial sac
but he believed that they were sensory, not motor. Markman (1958)
also reports the preseiice of sensory cells in the endostyle of Ciona
intestinulia but, shows the endostyle innervated from the visceral nervc.
In pelagic tutiicates Bone (1959) describes a pair of anterior visceral
nerves pttssing either side of the neural gland, passing the peripharpngeal band and innervating the endostyle. He speoulated that they may
perform a secreto-motor function. Fedelc (1923a) considered that the
interniittrnt beating of the branchial cilia is not directly controlled by
the visceral nerve and that special visceral nerve cells either on the gut
or perhaps in t,he pharynged wall itself must control this activity.
Bone (1959) was unable to substantiate this and Markman (1958)
concluded that all the gill slits are innervated from the paired posterior
nerves and not from the visceral syntem.
In two later papers Fedele (1927, 1938) described the visceral nervous system in Ciona and suggested that there may be a system fJf
autonomous nerve nets connected to the ganglion through the dorsal
strand. Surrounding the dorsal strand there seems to be a sheath of
nerve fibres and scattered nerve cells which Fedele considered to be of
‘‘ no less importance than the ganglion ” and which he believed provided
intestinal tract except for it smull sphincter muscle around the anus, and
there is little evidence to xuggt*st that any other part of the canal has a
special innervation.
(d) Gonadin1 activity. Thc gonads might be innervated by neurosecretory fibros and the sphincter rnuscle of the gonoduct may also be
subject to visceral innervation.
(e) Secrcto-motor activity. Various regions of the alimentary system,
and in particular the endostyle, are engaged in mucus secretion some of
which activity might be under viscero-motor control.
Fedele (1923a, 1927) reported the presence of a visceral plexus and
visceral nerve cells in Cionu and in the pelagic tunicate Salpa, but
neither Millar (1953a) nor Boric (1959) were able to find any nerve cells
on the gut of Ciona although Bone did find a few cells on the alimentary
canal of Salpa. In Cionu Bone found some multipolar stellate cells on
the gonoduct which had connwtions to the dorsal nerve but there is
nothing to enablc us to determine the function of these cells. Markman
(1958) was unable to locate any nerve cells outside of the dorsal ganglion
in young Ciona, and found no innervation at all in the intestine.
Innervation of the branchial sac and endostyle has been reported by
aeveral workers. Hunter ( I 898) illustrates nerve fibres from the anterior
region of the ganglion innervating tho endostyle and the branchial sac
but he believed that they were sensory, not motor. Markman (1958)
also reports the preseiice of sensory cells in the endostyle of Ciona
intestinulia but, shows the endostyle innervated from the visceral nervc.
In pelagic tutiicates Bone (1959) describes a pair of anterior visceral
nerves pttssing either side of the neural gland, passing the peripharpngeal band and innervating the endostyle. He speoulated that they may
perform a secreto-motor function. Fedelc (1923a) considered that the
interniittrnt beating of the branchial cilia is not directly controlled by
the visceral nerve and that special visceral nerve cells either on the gut
or perhaps in t,he pharynged wall itself must control this activity.
Bone (1959) was unable to substantiate this and Markman (1958)
concluded that all the gill slits are innervated from the paired posterior
nerves and not from the visceral syntem.
In two later papers Fedele (1927, 1938) described the visceral nervous system in Ciona and suggested that there may be a system fJf
autonomous nerve nets connected to the ganglion through the dorsal
strand. Surrounding the dorsal strand there seems to be a sheath of
nerve fibres and scattered nerve cells which Fedele considered to be of
‘‘ no less importance than the ganglion ” and which he believed provided