I). The pyloric !!land
The pyloric gland is t i system of tubules, terminating in small
swellings or ampullae, which ramify over and are closely applied to the
rdimentury canal lying bctweeii it and the connective tissue sheath
which surrounds it. ‘I’hc t,ubulcs unite to form a single pyloric duct
which usually opiis l),y a nrnidl q w r t i m into the alimentary canal at
tlhe juncttion of‘ the stomach t i r i d iutestine. In Ciona M i l k ( 1 953a)
described itJ oponing on t.lic? left,-tiiind side of the iinterior ciliated ring
of the iiitcstinc:. I n oertiiiu species of the fumily Didcmnidae the ramifying tubules arc til)wnt, tint1 thorc? ix t i large pyloria vesicle in the digestivv
loop ; i i singlo (luck c:tit(?rx this from the rcgioii of the intestinal wall and
;inother duct goes from the vesicle to the pyloric region of the stomach.
The most dctaileti account of thc morphology and histology of the
gland is given by E’ouque (1954) who suggests that it may have its
origin in a struoture like the siphon of the Echinoidea. From this it may
have evolved into its present complex form ~ t s
shown in Fig. 12. In the
most highly developed state as in Styelaplicata (Lesueur) the gland may
be divided into three morphological areas. Over the posterior end of
the intestine and rectum i t forms ramifying tubules and poorly developed ampullae, y d IL similar type of organization is also to be found
iiround the oesophagus. In the region of the mid-intestine the ampullae
me niorc iiiimeroiis and conspicuous and form what Fouque refers to as
the zone of contiguous impullsc. Throughout the gland the tubules
rind ampullae tire lincd b y IL single lu.vercd cuboidal epithelium. There
is considorrrblc! (!oiifiisioii in the litertiturc: ILR to whether these cells may
have cilia I)rojecting into thc? lunirn ofthc canal. Colton (1 91 0) describeH
the cell8 a x bearing long f h g e h , but AzBma ( 1 937) believed they had
small bundles of cilia. Millr~r (I!)ri3u) sttkt,eH that in Ciona the epithelium
bears “ a thin clothing of long cilia ”. Voucjue (1948) deHcriheH cilia
throughout the tubule in Biplosorrm hiits iii t i later paper (Fouque, 1054)
lie denied the existencc of cilia in t h c tubules and believed t h a t the
presence of oytoplanmic xtrtlndx in the lumen gave a false impreasion
of the presence of long cilia. There are, however, cilia in the pyloric
duct which beat, towards the alimentary canal.
Within the pyloric gland iind in particular in the region of contiguous
ampullae there is a cytonuclear cycle of events which has been described
similarly for Microcosmus. .sulcatus (Coquebert) by Az6ma (1937) and
for Styela plicata by Fouque (1 954). The similarity of events described
for the two species suggests that this is a normal cycle of events. In the
course of the cycle the oytoplasm becomes strongly basophile and
vitcuolated and the nuclkus contracts and expels chromatin which
The pyloric gland is t i system of tubules, terminating in small
swellings or ampullae, which ramify over and are closely applied to the
rdimentury canal lying bctweeii it and the connective tissue sheath
which surrounds it. ‘I’hc t,ubulcs unite to form a single pyloric duct
which usually opiis l),y a nrnidl q w r t i m into the alimentary canal at
tlhe juncttion of‘ the stomach t i r i d iutestine. In Ciona M i l k ( 1 953a)
described itJ oponing on t.lic? left,-tiiind side of the iinterior ciliated ring
of the iiitcstinc:. I n oertiiiu species of the fumily Didcmnidae the ramifying tubules arc til)wnt, tint1 thorc? ix t i large pyloria vesicle in the digestivv
loop ; i i singlo (luck c:tit(?rx this from the rcgioii of the intestinal wall and
;inother duct goes from the vesicle to the pyloric region of the stomach.
The most dctaileti account of thc morphology and histology of the
gland is given by E’ouque (1954) who suggests that it may have its
origin in a struoture like the siphon of the Echinoidea. From this it may
have evolved into its present complex form ~ t s
shown in Fig. 12. In the
most highly developed state as in Styelaplicata (Lesueur) the gland may
be divided into three morphological areas. Over the posterior end of
the intestine and rectum i t forms ramifying tubules and poorly developed ampullae, y d IL similar type of organization is also to be found
iiround the oesophagus. In the region of the mid-intestine the ampullae
me niorc iiiimeroiis and conspicuous and form what Fouque refers to as
the zone of contiguous impullsc. Throughout the gland the tubules
rind ampullae tire lincd b y IL single lu.vercd cuboidal epithelium. There
is considorrrblc! (!oiifiisioii in the litertiturc: ILR to whether these cells may
have cilia I)rojecting into thc? lunirn ofthc canal. Colton (1 91 0) describeH
the cell8 a x bearing long f h g e h , but AzBma ( 1 937) believed they had
small bundles of cilia. Millr~r (I!)ri3u) sttkt,eH that in Ciona the epithelium
bears “ a thin clothing of long cilia ”. Voucjue (1948) deHcriheH cilia
throughout the tubule in Biplosorrm hiits iii t i later paper (Fouque, 1054)
lie denied the existencc of cilia in t h c tubules and believed t h a t the
presence of oytoplanmic xtrtlndx in the lumen gave a false impreasion
of the presence of long cilia. There are, however, cilia in the pyloric
duct which beat, towards the alimentary canal.
Within the pyloric gland iind in particular in the region of contiguous
ampullae there is a cytonuclear cycle of events which has been described
similarly for Microcosmus. .sulcatus (Coquebert) by Az6ma (1937) and
for Styela plicata by Fouque (1 954). The similarity of events described
for the two species suggests that this is a normal cycle of events. In the
course of the cycle the oytoplasm becomes strongly basophile and
vitcuolated and the nuclkus contracts and expels chromatin which