289
them. Ostroumoff ( 1886b , c , p. 561,) subsequently wrote
that “sexes are usually separated” in zooids of Tendra .
Repiachoff found ovaries on the basal wall in zooids with
normal morphology as well as in those with brood chambers,
and confi rmed the data of Claparède ( 1871 ) on the early
appearance of the ovary in young zooids with developing
polypides; he described and depicted the incipient ovary
adjacent to the polypide bud. The mature ovary contained up
to ten oocytes, being surrounded by a membrane [ovarian
wall]. Ovulated oocytes (up to three) remained in the perigastric coelom for some time until oviposition. Repiachoff
also described and illustrated larval structure, metamorphosis and development of the ancestrula in detail (see also
Repiachoff 1878 ).
Although not understanding the actual structure of zooids
with acanthostegal brood chambers, Repiahoff ( 1875 ) suggested that they play a role similar to that of ovicells.
Following him (and Nordmann 1839 ), Reinhard ( 1875 )
thought that embryos developed inside the body cavity of
these specialized zooids in this species. However, he believed
that they could not be compared with ovicells since they possessed a polypide and an ovary. Reinhard criticized the statement of Nordmann ( 1839 ), who thought that sperm could
enter female zooids through opening in the [transverse] wall
between subsequent zooids. He also challenged the opinion
of Salensky ( 1874 ) on ovary structure (see above), stating
that there were not two layers and that it exhibited a gradual
change in shape and size from large and roundish cells in the
middle to smaller elongated cells at the periphery. Reinhard
recorded spermatogenic tissue developing on both lateral
walls and proximally in the cystid, and an ovary lying on the
basal wall either in the middle or in the proximal half of the
fertile zooid. He was possibly the fi rst to describe clusters of
spermatozoids (spermatozeugmata), which, as he surmised,
result from the grouping of originally single “seminal
threads” with elongated heads. He further described and
depicted aspects of egg and sperm formation not only in
Tendra , but also in Cryptosula pallasiana and Smittoidea
reticulata (both as Lepralia ).
Ostroumoff ( 1886b , c ) was the fi rst to recognize the
actual position of the developing embryos in the space [epistege] between the frontal membrane and the overarching
spines in brooding zooids of T . zostericola . Later
Paltschikowa-Ostroumowa ( 1926 ) and Braiko ( 1967 )
described oviposition via the intertentacular organ, and the
tentacle crown entering the epistege in this species. The
intertentacular organ was discovered fi rst by PaltschikowaOstroumowa in both T . zostericola and Electra repiachowi
(as Membranipora ), often considered to be the same species by previous authors. Paltschikowa-Ostroumowa suggested that the formation of the acanthostegal brood- chamber
by the distal zooid is infl uenced by hormones produced by
the maternal zooid in the former species.
Using Cryptosula pallasiana (as Lepralia ), Repiachoff
( 1876 ) described the cheilostome ovary more precisely. He
observed that the ovary is situated in the distal part of zooid
on the basal wall, being in “genetic connection” with the
“Endocyste”. Eggs are surrounded by (1) a thin cellular layer
(interpreted as a “cell membrane” [= ovary wall]) that is connected with (2) a group of cells forming the base of the ovary.
Describing sperm, he differentiated between thin and thick
moving “threads” [spermatozoids and spermatozeugmata],
and even asked if the latter consist of several of the former.
Cleavage, larval structure and development of the ancestrula
were also studied in the same work.
Repiachoff ( 1876 ) also briefl y described and depicted
oocytes in the ovary of Electra repiachowi (as Tendra ). It is
particularly interesting that some of the oocytes were lobate.
Sperm were also detected. Noteworthy, Ostroumoff ( 1886b , c )
stressed that spermatozoids form bundles [spermatozeugmata?], reminiscent of tiny nematodes, in the latter species
whereas they were single in T. zostericola . He further noted
that the ovary is situated “near opercular surface [frontal
wall]” in Tendra ( 1886b , p. 18), and “near basal surface
[wall]” in E. repiachowi (p. 20). According to his description, zooids are hermaphrodite in the latter. Ostroumoff
( 1886b ) also stated that the larva develops inside the tentacle
sheath in Cryptosula pallasiana .
Ehlers’s ( 1876 ) study of the ctenostome bryozoan
Hypophorella expansa showed that both male and female
gonads occur on the internal surface of the body wall of the
same zooid. He described spermato- and oogenesis, being
one of the fi rst to make measurements of spermatozoids,
ovaries and eggs, the latter at different stages of development. Ehlers observed up to 30 growing oocytes in the ovary,
suggesting that the later-developed ones would develop after
the ovulation of those developed earlier. He also noted a
structure that he fi rst thought was “Ausführungsapparat”
[intertentacular organ] in the retracted polypide of
Hypophorella , and stated that he saw it in almost all zooids
in a non-identifi ed cheilostome (as Lepralia ). However,
although knowing about the similar fi ndings of Farre ( 1837 )
and Hincks ( 1851 ), Ehlers decided that it was a parasitic
infusorian. Later Prouho ( 1892 ) showed that there is a supraneural pore in H . expansa .
One of the most informative and infl uential (but almost
forgotten) papers of that time was published by Joliet ( 1877a ).
This author observed gametogenesis in ten gymnolaemate
bryozoans, both cheilostome and ctenostome. He stated that
formation of the sex cells is connected with a polypide,
showing that both testes and ovaries are formed at the
expense of the funiculus. In hermaphrodite zooids the ovary
is placed in the upper part [of the funiculus] near the caecum, and the testis in its lower part. In gonochoristic zooids
the gonad is situated where the funiculus approaches the
cystid wall, connecting with its funicular network. Thus,
Appendices
them. Ostroumoff ( 1886b , c , p. 561,) subsequently wrote
that “sexes are usually separated” in zooids of Tendra .
Repiachoff found ovaries on the basal wall in zooids with
normal morphology as well as in those with brood chambers,
and confi rmed the data of Claparède ( 1871 ) on the early
appearance of the ovary in young zooids with developing
polypides; he described and depicted the incipient ovary
adjacent to the polypide bud. The mature ovary contained up
to ten oocytes, being surrounded by a membrane [ovarian
wall]. Ovulated oocytes (up to three) remained in the perigastric coelom for some time until oviposition. Repiachoff
also described and illustrated larval structure, metamorphosis and development of the ancestrula in detail (see also
Repiachoff 1878 ).
Although not understanding the actual structure of zooids
with acanthostegal brood chambers, Repiahoff ( 1875 ) suggested that they play a role similar to that of ovicells.
Following him (and Nordmann 1839 ), Reinhard ( 1875 )
thought that embryos developed inside the body cavity of
these specialized zooids in this species. However, he believed
that they could not be compared with ovicells since they possessed a polypide and an ovary. Reinhard criticized the statement of Nordmann ( 1839 ), who thought that sperm could
enter female zooids through opening in the [transverse] wall
between subsequent zooids. He also challenged the opinion
of Salensky ( 1874 ) on ovary structure (see above), stating
that there were not two layers and that it exhibited a gradual
change in shape and size from large and roundish cells in the
middle to smaller elongated cells at the periphery. Reinhard
recorded spermatogenic tissue developing on both lateral
walls and proximally in the cystid, and an ovary lying on the
basal wall either in the middle or in the proximal half of the
fertile zooid. He was possibly the fi rst to describe clusters of
spermatozoids (spermatozeugmata), which, as he surmised,
result from the grouping of originally single “seminal
threads” with elongated heads. He further described and
depicted aspects of egg and sperm formation not only in
Tendra , but also in Cryptosula pallasiana and Smittoidea
reticulata (both as Lepralia ).
Ostroumoff ( 1886b , c ) was the fi rst to recognize the
actual position of the developing embryos in the space [epistege] between the frontal membrane and the overarching
spines in brooding zooids of T . zostericola . Later
Paltschikowa-Ostroumowa ( 1926 ) and Braiko ( 1967 )
described oviposition via the intertentacular organ, and the
tentacle crown entering the epistege in this species. The
intertentacular organ was discovered fi rst by PaltschikowaOstroumowa in both T . zostericola and Electra repiachowi
(as Membranipora ), often considered to be the same species by previous authors. Paltschikowa-Ostroumowa suggested that the formation of the acanthostegal brood- chamber
by the distal zooid is infl uenced by hormones produced by
the maternal zooid in the former species.
Using Cryptosula pallasiana (as Lepralia ), Repiachoff
( 1876 ) described the cheilostome ovary more precisely. He
observed that the ovary is situated in the distal part of zooid
on the basal wall, being in “genetic connection” with the
“Endocyste”. Eggs are surrounded by (1) a thin cellular layer
(interpreted as a “cell membrane” [= ovary wall]) that is connected with (2) a group of cells forming the base of the ovary.
Describing sperm, he differentiated between thin and thick
moving “threads” [spermatozoids and spermatozeugmata],
and even asked if the latter consist of several of the former.
Cleavage, larval structure and development of the ancestrula
were also studied in the same work.
Repiachoff ( 1876 ) also briefl y described and depicted
oocytes in the ovary of Electra repiachowi (as Tendra ). It is
particularly interesting that some of the oocytes were lobate.
Sperm were also detected. Noteworthy, Ostroumoff ( 1886b , c )
stressed that spermatozoids form bundles [spermatozeugmata?], reminiscent of tiny nematodes, in the latter species
whereas they were single in T. zostericola . He further noted
that the ovary is situated “near opercular surface [frontal
wall]” in Tendra ( 1886b , p. 18), and “near basal surface
[wall]” in E. repiachowi (p. 20). According to his description, zooids are hermaphrodite in the latter. Ostroumoff
( 1886b ) also stated that the larva develops inside the tentacle
sheath in Cryptosula pallasiana .
Ehlers’s ( 1876 ) study of the ctenostome bryozoan
Hypophorella expansa showed that both male and female
gonads occur on the internal surface of the body wall of the
same zooid. He described spermato- and oogenesis, being
one of the fi rst to make measurements of spermatozoids,
ovaries and eggs, the latter at different stages of development. Ehlers observed up to 30 growing oocytes in the ovary,
suggesting that the later-developed ones would develop after
the ovulation of those developed earlier. He also noted a
structure that he fi rst thought was “Ausführungsapparat”
[intertentacular organ] in the retracted polypide of
Hypophorella , and stated that he saw it in almost all zooids
in a non-identifi ed cheilostome (as Lepralia ). However,
although knowing about the similar fi ndings of Farre ( 1837 )
and Hincks ( 1851 ), Ehlers decided that it was a parasitic
infusorian. Later Prouho ( 1892 ) showed that there is a supraneural pore in H . expansa .
One of the most informative and infl uential (but almost
forgotten) papers of that time was published by Joliet ( 1877a ).
This author observed gametogenesis in ten gymnolaemate
bryozoans, both cheilostome and ctenostome. He stated that
formation of the sex cells is connected with a polypide,
showing that both testes and ovaries are formed at the
expense of the funiculus. In hermaphrodite zooids the ovary
is placed in the upper part [of the funiculus] near the caecum, and the testis in its lower part. In gonochoristic zooids
the gonad is situated where the funiculus approaches the
cystid wall, connecting with its funicular network. Thus,
Appendices