285
(p. 22). Ellis also mentioned the suggestion of Pallas ( 1766 )
concerning ovicells (“pearl-like fi gures”) and avicularia as
“Nectariums, analogous to what is so called in the fl owers of
some plants” (p. 20).
Nineteenth Century: Primary Accumulation
of Data and First Reviews
The suggestion that ovicells are ovaria was accepted and not
reconsidered for almost a century (see Lamouroux 1816 ;
Milne Edwards 1836 ; de Lamarck 1836 ; Reid 1845 ;
Johnston 1847 ; Landsborough 1852 ; Hincks 1861 , 1873 ,
1880 ). However, an accumulation of data on other bryozoan
groups, whose representatives had no ovicells (ctenostomes
as well as some non-ovicellate cheilostomes), contradicted
the traditional point of view. For instance, Thompson ( 1830 ,
p. 96) observed “an ovum or ovarium” on the body wall
inside the autozooid of “ Vesicularia ”, and Milne-Edwards
( 1836 ) also mentioned it on the zooidal wall in “ Cellariae ”.
Additionally, some researchers considered brown bodies to
be a special kind of egg, fi nding them in zooids with degenerated polypides (Hincks 1861 ; Bronn 1862 ; reviewed in
Hincks 1873 ).
It should be noted here that microanatomical sectioning
techniques had not been used by researchers studying
Bryozoa until the last third of the nineteenth century.
Therefore, earlier observations on internal structure were
restricted to species having a transparent body wall. Besides,
the strongest magnifi cation available at that time could not
be used with thick preparations, whether the tissues were living or fi xed. On the other hand, such observations allowed
three-dimensional reconstructions of the animals studied and
records were made from specimens that were often still alive.
One of the fi rst detailed descriptions of sexual reproduction in marine bryozoans was made by Grant ( 1827 , p. 116),
who also discussed the data and statements of the previous
authors (Basteri 1762 ; Pallas 1766 ; Lamouroux 1816 ; de
Lamarck 1816 ). His paper was one of the most valuable and
precise sources of information on this topic for a long time.
Studying the cheilostomes Carbasea carbasea (as Flustra )
and Flustra foliacea , he found a young “ovum … as a small
yellow point” developing inside the zooid and being unconnected with the polypide. Grant wrote then that such eggs
“appear to be produced by the posterior wall of the cell”
[basal cystid wall] in the fi rst species. He was not aware that
C . carbasea is an internal brooder whose embryos develop in
a brood sac. That is why he described oocyte growth (occurring in the perivisceral coelom “a little below the aperture of
the cell, and behind the body of the polypus”) and larval
development as a single process of intrazooidal “ovum
development”, accompanied by polypide degeneration. It
was supposed that regeneration took place after release of
the ciliated “ovum” [larva] that occupied one third of the
cystid volume. Grant carefully described the pattern of distribution of egg-bearing zooids throughout the colony. He followed the release of larvae, their swimming behaviour and
settlement. He was probably the fi rst to describe larval metamorphosis and ancestrula formation in cheilostomes.
In F . foliacea , young “pale-red ova” are said to develop in
the proximal part of zooids in which “the polypi … are generally removed [degenerated]” (Grant 1827 , p. 341). The
mature ovum [embryo] occupies the distal part of the cystid,
becoming surrounded by “a distinct wide helmet-shaped
capsule [ooecium of endozooidal ovicell]” that separates “it
from the cavity of the cell [zooid]”. Grant observed moving
larvae inside the brood chamber, their release, settlement and
metamorphosis. The polypide regenerates when the “ovum
has escaped from the cell” and the same zooid repeatedly
“produce[s] the ova and polypi” ( 1827 , pp. 341–342). Grant
may also have observed spermatozoids; he ambiguously
wrote of “numerous monads and other animalcules busily
employed in consuming the remains of the dead [degenerated] polypus” (p. 117).
Farre ( 1837 ) discovered, illustrated and described in
detail an intertentacular organ and the movements of its cilia
in the ctenostome Alcyonidium duplex (as Halodactylus
diaphanus ), and also recorded and depicted it in the cheilostome Electra pilosa (as Membranipora ). This author did not
recognize its function, but asked the question “does it indicate a difference of sex?” (p. 408). He was obviously the fi rst
to describe and depict spermatozoids moving inside the
zooid cavity in A . duplex and Walkeria uva (as Valkeria cuscuta ) and even saw sperm release in the fi rst species. Farre
called the male cells “parasites” and “cercariae”, however,
not being able to ascertain the exact locus of their expulsion
since the polypide was half-retracted. In particular, it was
written that they “issued from the centre of the tentacula” (p.
409). Based on this observation, Farre correctly supposed the
existence of some form of communication between the body
cavity and the external medium. Four to six embryos (“ciliated gemmules”) were found brooded internally in the
“transparent sac” of A . duplex . Additionally, two kinds of
“rounded or oval bodies” – brown [obviously, brown bodies]
and “milky-white”, were recorded inside the zooid cavity of
Bowerbankia imbricata (as B . densa ). Farre tended to believe
that both were connected “with the process of reproduction”,
but doubted if they were “ovaries or … immature ova” (pp.
400–401).
Based on the presence of sperm, eggs and embryos in
zooids with acanthostegal (spinous) brood chambers,
Nordmann ( 1839 ) described male zooids (“cellules males”)
and female zooids (“cellules femelles”) in the cheilostome
Tendra zostericola . He suggested that spermatozoids fertilize eggs intracolonially, entering female zooids via the
“opening in the base of every cell” [zooid] (p. 191). This
author also observed eggs (from four to seven per zooid),
developing embryos and mature larvae rotating inside a
Appendices
(p. 22). Ellis also mentioned the suggestion of Pallas ( 1766 )
concerning ovicells (“pearl-like fi gures”) and avicularia as
“Nectariums, analogous to what is so called in the fl owers of
some plants” (p. 20).
Nineteenth Century: Primary Accumulation
of Data and First Reviews
The suggestion that ovicells are ovaria was accepted and not
reconsidered for almost a century (see Lamouroux 1816 ;
Milne Edwards 1836 ; de Lamarck 1836 ; Reid 1845 ;
Johnston 1847 ; Landsborough 1852 ; Hincks 1861 , 1873 ,
1880 ). However, an accumulation of data on other bryozoan
groups, whose representatives had no ovicells (ctenostomes
as well as some non-ovicellate cheilostomes), contradicted
the traditional point of view. For instance, Thompson ( 1830 ,
p. 96) observed “an ovum or ovarium” on the body wall
inside the autozooid of “ Vesicularia ”, and Milne-Edwards
( 1836 ) also mentioned it on the zooidal wall in “ Cellariae ”.
Additionally, some researchers considered brown bodies to
be a special kind of egg, fi nding them in zooids with degenerated polypides (Hincks 1861 ; Bronn 1862 ; reviewed in
Hincks 1873 ).
It should be noted here that microanatomical sectioning
techniques had not been used by researchers studying
Bryozoa until the last third of the nineteenth century.
Therefore, earlier observations on internal structure were
restricted to species having a transparent body wall. Besides,
the strongest magnifi cation available at that time could not
be used with thick preparations, whether the tissues were living or fi xed. On the other hand, such observations allowed
three-dimensional reconstructions of the animals studied and
records were made from specimens that were often still alive.
One of the fi rst detailed descriptions of sexual reproduction in marine bryozoans was made by Grant ( 1827 , p. 116),
who also discussed the data and statements of the previous
authors (Basteri 1762 ; Pallas 1766 ; Lamouroux 1816 ; de
Lamarck 1816 ). His paper was one of the most valuable and
precise sources of information on this topic for a long time.
Studying the cheilostomes Carbasea carbasea (as Flustra )
and Flustra foliacea , he found a young “ovum … as a small
yellow point” developing inside the zooid and being unconnected with the polypide. Grant wrote then that such eggs
“appear to be produced by the posterior wall of the cell”
[basal cystid wall] in the fi rst species. He was not aware that
C . carbasea is an internal brooder whose embryos develop in
a brood sac. That is why he described oocyte growth (occurring in the perivisceral coelom “a little below the aperture of
the cell, and behind the body of the polypus”) and larval
development as a single process of intrazooidal “ovum
development”, accompanied by polypide degeneration. It
was supposed that regeneration took place after release of
the ciliated “ovum” [larva] that occupied one third of the
cystid volume. Grant carefully described the pattern of distribution of egg-bearing zooids throughout the colony. He followed the release of larvae, their swimming behaviour and
settlement. He was probably the fi rst to describe larval metamorphosis and ancestrula formation in cheilostomes.
In F . foliacea , young “pale-red ova” are said to develop in
the proximal part of zooids in which “the polypi … are generally removed [degenerated]” (Grant 1827 , p. 341). The
mature ovum [embryo] occupies the distal part of the cystid,
becoming surrounded by “a distinct wide helmet-shaped
capsule [ooecium of endozooidal ovicell]” that separates “it
from the cavity of the cell [zooid]”. Grant observed moving
larvae inside the brood chamber, their release, settlement and
metamorphosis. The polypide regenerates when the “ovum
has escaped from the cell” and the same zooid repeatedly
“produce[s] the ova and polypi” ( 1827 , pp. 341–342). Grant
may also have observed spermatozoids; he ambiguously
wrote of “numerous monads and other animalcules busily
employed in consuming the remains of the dead [degenerated] polypus” (p. 117).
Farre ( 1837 ) discovered, illustrated and described in
detail an intertentacular organ and the movements of its cilia
in the ctenostome Alcyonidium duplex (as Halodactylus
diaphanus ), and also recorded and depicted it in the cheilostome Electra pilosa (as Membranipora ). This author did not
recognize its function, but asked the question “does it indicate a difference of sex?” (p. 408). He was obviously the fi rst
to describe and depict spermatozoids moving inside the
zooid cavity in A . duplex and Walkeria uva (as Valkeria cuscuta ) and even saw sperm release in the fi rst species. Farre
called the male cells “parasites” and “cercariae”, however,
not being able to ascertain the exact locus of their expulsion
since the polypide was half-retracted. In particular, it was
written that they “issued from the centre of the tentacula” (p.
409). Based on this observation, Farre correctly supposed the
existence of some form of communication between the body
cavity and the external medium. Four to six embryos (“ciliated gemmules”) were found brooded internally in the
“transparent sac” of A . duplex . Additionally, two kinds of
“rounded or oval bodies” – brown [obviously, brown bodies]
and “milky-white”, were recorded inside the zooid cavity of
Bowerbankia imbricata (as B . densa ). Farre tended to believe
that both were connected “with the process of reproduction”,
but doubted if they were “ovaries or … immature ova” (pp.
400–401).
Based on the presence of sperm, eggs and embryos in
zooids with acanthostegal (spinous) brood chambers,
Nordmann ( 1839 ) described male zooids (“cellules males”)
and female zooids (“cellules femelles”) in the cheilostome
Tendra zostericola . He suggested that spermatozoids fertilize eggs intracolonially, entering female zooids via the
“opening in the base of every cell” [zooid] (p. 191). This
author also observed eggs (from four to seven per zooid),
developing embryos and mature larvae rotating inside a
Appendices