118
ooecial vesicle, giving a detailed description of its musculature,
which consisted of two perpendicular groups of bands. He
thought that one of the muscle groups was responsible for the
rupture of the wall of the ooecial vesicle during oviposition.
Jullien ( 1888 , p. 1.56) used the terms “coїtis” (Greek,
“cradle”) for the thick external ovicellar wall [ectooecium]
and “sparganile” (Greek, “swaddling-cloth”) [entooecium]
for the thin internal wall in his description of the cheilostome
Exochella longirostris (see also Jullien and Calvet 1903 ).
In classifying cheilostomes, he introduced the new “tribes”
Inovicellata, Subovicellata and Superovicellata based on the
presence/absence of the ovicells and position of the ovicell
opening in relation to the orifi ce of the maternal autozooid,
and was the fi rst to propose new terms for the different types of
ovicell closure, dividing cheilostomes into “aneucleithrien(s)”
(with ovicells not closed by the zooidal operculum) and
“cleithrien(s)” (with ovicells closed by it) (see also Canu
and Bassler 1920 ). These terms were subsequently modifi ed
to “acleithral” and “cleithral” by Ryland ( 1968 ).
Delage and Hérouard ( 1897 ) cited both Nitsche’s ( 1869 )
opinion that brood chambers were formed by the maternal
zooid and Vigelius’s ( 1884a ) view that maternal and daughter
zooids might both be involved in ovicell formation, favouring
the former. Harmer ( 1902 , p. 284) was the fi rst to consider
three possibilities concerning ovicell [meaning its protective
capsule, ooecium] development: the “ovicell” can (1) belong
to the “fertile (proximal)” zooid, (2) belong to the “distal”
zooid, or (3) be “a modifi ed individual, as believed by
Nitsche and others”. In describing the ooecium in Euthyroides
episcopalis , Harmer suggested (but did not prove) that “the
ovicell is formed by the fusion of a pair of greatly expanded
oral spines, the bases of which should communicate with
the fertile zooecium on each side of the operculum” of the
maternal zooid ( 1902 , p. 283). He also stressed that “it is
impossible not to be struck by the resemblance between
the development of the ovicell and that of the frontal bars”
[zooidal costae] in this species.
Waters ( 1889 , 1904 , 1907 , 1909 , 1912 , 1913 ) made sections of ovicells in a number of cheilostome species. While
his descriptions and fi gures showed that there are two ways
of forming ooecia, either from the maternal or the daughter
zooid, he did not discuss this distinction. In his study of
tube-like brood chambers (“peristomial ooecia” in the terminology of Levinsen 1902 ) in Margaretta chuakensis (as
Tubucellaria ceroides var. chuakensis ), Waters ( 1907 )
found a peculiar modifi ed polypide with a special terminal
plug closing the entrance to the ovicell. In his paper briefl y
describing and illustrating ovicell formation in Bugula neritina (Waters 1909 ), he also mentioned that “the ovum
passes for development into a sac at the distal end by the
basal wall” in Watersipora cucullata (as Lepralia ). He
called this internal brood sac “a concealed ovicell”
(p. 151). Waters ( 1913 ) depicted the ovicell of Halysisis
diaphanus (as Catenaria diaphana ) as consisting of a
small kenozooidal ooecium (budded from the fertile zooid)
and brood sac. In this paper he also applied the characters of ovicell shape and position to the classifi cation of
Catenicellidae and described the developmental stages of
the ovicell in Triphyllozoon (as Retepora monilifera var.
umbonata ). The latter data were further supported and
verifi ed by Okada ( 1920 ), Buchner ( 1924 ) and Harmer
( 1934 ), who described ovicellogenesis in several confamilial species of Phidoloporidae.
Calvet ( 1900 ) carefully investigated the anatomy of
brood chambers in a number of marine bryozoans, including
cheilostomes, making sections of decalcifi ed specimens.
He noted that, compared to the majority of cheilostomes and
ctenostomes that incubate their offspring, there are some that
do not. In Bugula simplex (as B . sabatieri ) he described early
ovicellogenesis as the formation of two hollow vesicles, one
of which, formed from a maternal zooid, was a rudiment of the
ooecial vesicle (“vésicule ovicellienne inférieure”), whereas
the second, originating from a daughter zooid, was a rudiment of the ooecium (“vésicule ovicellienne supérieure”)
(Calvet 1900 , p. 132; p. 57, fi g. 10; pl. 2, fi g. 14; pl. 3,
fi gs. 5–6). Calvet suggested that this ovicell type, in which
two parts of the ovicell (ooecium and inner vesicle) belong to
different subsequent zooids, is the commonest among cheilostomes. He thought that Bicellariella ciliata , the ovicells of
which were studied by Nitsche ( 1869 ), should not be an
exception to this rule. A recent study has confi rmed the correctness of Calvet’s suggestion (Moosburgger et al. 2012 ).
One of Calvet’s most important fi ndings was a communication pore in the septum between ooecial and
daughter- zooid coeloms (Calvet 1900 , p. 58, fi g. 10)
(Fig. 2.3 ). Unfortunately, this communication, which was
conclusive evidence of ooecial formation from the distal
zooid, was overlooked or ignored by most subsequent
authors. In the ooecial vesicle of B. simplex Calvet found a
sclerite (a thickening of the cuticle corresponding to the zone
of contact between the ooecium and ooecial vesicle), a
plexus of mesenchymatous cells (funicular strands), and,
similar to Vigelius ( 1886 ), musculature and embryophore.
He described and illustrated the structure of the endozooidal
ovicell in Securifl ustra securifrons (as Flustra ), depicting
longitudinal sections of the hyperstomial ovicells of
Amphiblestrum fl emingi (as Membranipora ) and Fenestrulina
malusii (as Microporella ).
Until now, Calvet ( 1900 ) remains the only researcher to
have studied the anatomy of endotoichal ovicells in the genus
Cellaria (in Cellaria fi stulosa and C. salicornioides ). One
of the most interesting characters found in these peculiar
internal brood chambers was an additional operculum
(actually, part of the modifi ed ooecial vesicle), closing the
ovicell opening. Calvet wrote that the brood cavity [as he
called the space around the brood sac] is connected with
2 Cheilostome Brood Chambers: Structure, Formation, Evolution
ooecial vesicle, giving a detailed description of its musculature,
which consisted of two perpendicular groups of bands. He
thought that one of the muscle groups was responsible for the
rupture of the wall of the ooecial vesicle during oviposition.
Jullien ( 1888 , p. 1.56) used the terms “coїtis” (Greek,
“cradle”) for the thick external ovicellar wall [ectooecium]
and “sparganile” (Greek, “swaddling-cloth”) [entooecium]
for the thin internal wall in his description of the cheilostome
Exochella longirostris (see also Jullien and Calvet 1903 ).
In classifying cheilostomes, he introduced the new “tribes”
Inovicellata, Subovicellata and Superovicellata based on the
presence/absence of the ovicells and position of the ovicell
opening in relation to the orifi ce of the maternal autozooid,
and was the fi rst to propose new terms for the different types of
ovicell closure, dividing cheilostomes into “aneucleithrien(s)”
(with ovicells not closed by the zooidal operculum) and
“cleithrien(s)” (with ovicells closed by it) (see also Canu
and Bassler 1920 ). These terms were subsequently modifi ed
to “acleithral” and “cleithral” by Ryland ( 1968 ).
Delage and Hérouard ( 1897 ) cited both Nitsche’s ( 1869 )
opinion that brood chambers were formed by the maternal
zooid and Vigelius’s ( 1884a ) view that maternal and daughter
zooids might both be involved in ovicell formation, favouring
the former. Harmer ( 1902 , p. 284) was the fi rst to consider
three possibilities concerning ovicell [meaning its protective
capsule, ooecium] development: the “ovicell” can (1) belong
to the “fertile (proximal)” zooid, (2) belong to the “distal”
zooid, or (3) be “a modifi ed individual, as believed by
Nitsche and others”. In describing the ooecium in Euthyroides
episcopalis , Harmer suggested (but did not prove) that “the
ovicell is formed by the fusion of a pair of greatly expanded
oral spines, the bases of which should communicate with
the fertile zooecium on each side of the operculum” of the
maternal zooid ( 1902 , p. 283). He also stressed that “it is
impossible not to be struck by the resemblance between
the development of the ovicell and that of the frontal bars”
[zooidal costae] in this species.
Waters ( 1889 , 1904 , 1907 , 1909 , 1912 , 1913 ) made sections of ovicells in a number of cheilostome species. While
his descriptions and fi gures showed that there are two ways
of forming ooecia, either from the maternal or the daughter
zooid, he did not discuss this distinction. In his study of
tube-like brood chambers (“peristomial ooecia” in the terminology of Levinsen 1902 ) in Margaretta chuakensis (as
Tubucellaria ceroides var. chuakensis ), Waters ( 1907 )
found a peculiar modifi ed polypide with a special terminal
plug closing the entrance to the ovicell. In his paper briefl y
describing and illustrating ovicell formation in Bugula neritina (Waters 1909 ), he also mentioned that “the ovum
passes for development into a sac at the distal end by the
basal wall” in Watersipora cucullata (as Lepralia ). He
called this internal brood sac “a concealed ovicell”
(p. 151). Waters ( 1913 ) depicted the ovicell of Halysisis
diaphanus (as Catenaria diaphana ) as consisting of a
small kenozooidal ooecium (budded from the fertile zooid)
and brood sac. In this paper he also applied the characters of ovicell shape and position to the classifi cation of
Catenicellidae and described the developmental stages of
the ovicell in Triphyllozoon (as Retepora monilifera var.
umbonata ). The latter data were further supported and
verifi ed by Okada ( 1920 ), Buchner ( 1924 ) and Harmer
( 1934 ), who described ovicellogenesis in several confamilial species of Phidoloporidae.
Calvet ( 1900 ) carefully investigated the anatomy of
brood chambers in a number of marine bryozoans, including
cheilostomes, making sections of decalcifi ed specimens.
He noted that, compared to the majority of cheilostomes and
ctenostomes that incubate their offspring, there are some that
do not. In Bugula simplex (as B . sabatieri ) he described early
ovicellogenesis as the formation of two hollow vesicles, one
of which, formed from a maternal zooid, was a rudiment of the
ooecial vesicle (“vésicule ovicellienne inférieure”), whereas
the second, originating from a daughter zooid, was a rudiment of the ooecium (“vésicule ovicellienne supérieure”)
(Calvet 1900 , p. 132; p. 57, fi g. 10; pl. 2, fi g. 14; pl. 3,
fi gs. 5–6). Calvet suggested that this ovicell type, in which
two parts of the ovicell (ooecium and inner vesicle) belong to
different subsequent zooids, is the commonest among cheilostomes. He thought that Bicellariella ciliata , the ovicells of
which were studied by Nitsche ( 1869 ), should not be an
exception to this rule. A recent study has confi rmed the correctness of Calvet’s suggestion (Moosburgger et al. 2012 ).
One of Calvet’s most important fi ndings was a communication pore in the septum between ooecial and
daughter- zooid coeloms (Calvet 1900 , p. 58, fi g. 10)
(Fig. 2.3 ). Unfortunately, this communication, which was
conclusive evidence of ooecial formation from the distal
zooid, was overlooked or ignored by most subsequent
authors. In the ooecial vesicle of B. simplex Calvet found a
sclerite (a thickening of the cuticle corresponding to the zone
of contact between the ooecium and ooecial vesicle), a
plexus of mesenchymatous cells (funicular strands), and,
similar to Vigelius ( 1886 ), musculature and embryophore.
He described and illustrated the structure of the endozooidal
ovicell in Securifl ustra securifrons (as Flustra ), depicting
longitudinal sections of the hyperstomial ovicells of
Amphiblestrum fl emingi (as Membranipora ) and Fenestrulina
malusii (as Microporella ).
Until now, Calvet ( 1900 ) remains the only researcher to
have studied the anatomy of endotoichal ovicells in the genus
Cellaria (in Cellaria fi stulosa and C. salicornioides ). One
of the most interesting characters found in these peculiar
internal brood chambers was an additional operculum
(actually, part of the modifi ed ooecial vesicle), closing the
ovicell opening. Calvet wrote that the brood cavity [as he
called the space around the brood sac] is connected with
2 Cheilostome Brood Chambers: Structure, Formation, Evolution