286
“chorion” [fertilization envelope] in the brood chamber.
Nordmann also observed swimming larvae and mentioned
their settlement, followed by development of the ancestrula.
Johnston ( 1838 ) briefl y discussed the known facts on
bryozoan reproduction in the fi rst edition of his famous
monograph “A history of the British zoophytes”. He mainly
followed and widely cited the paper of Grant ( 1827 ), writing
that “the ova formed in the cells [zooids]” (p. 47).
Some observations of Farre ( 1837 ) were restated and
explained by Hincks ( 1851 ), who described the structure of
the ciliary intertentacular organ in the cheilostome Electra
pilosa (as Membranipora ) and recorded sperm release
through it. This is in contradiction with the more recent
observations of Silén ( 1966 ), who described sperm release
through the pores in the tips of the tentacles in two other species of Electra (see below). However, the description of
Hincks is so detailed and convincing that one can be left in
no doubt whether sperm expulsion may really be sometimes
possible through the intertentacular organ in E. pilosa . In
connection with this, Prouho ( 1892 ) suggested that this could
happen if the rest of the sperm [remaining after intrazooidal
self-fertilization] exited at the end of the reproductive period.
Hincks suggested that the intertentacular organ could also be
used for the release of eggs after their ovulation and fertilization in the body cavity, and this was later proven by Prouho
( 1889 ), who described egg liberation in the ctenostome
Alcyonidium albidum . Additionally, Hincks ( 1851 ) observed
sperm in Bowerbankia sp. and larval release in A . hirsutum
(as Cycloum papillosum ).
Kölliker ( 1841 ) recorded the presence of eggs and sperm
in Alcyonidium sp. (as A . gelatinosum ) and pointed out that
the “cercariae” of Farre were spermatozoids, which Kölliker
described, measured and precisely depicted. He believed that
the gonads were contained not inside the zooids, but between
them in the branches of the colony.
Hassall ( 1841 ) observed developing embryos, which he
called “ciliated eggs”, in groups of six or seven arranged in a
circle in Alcyonidium hirsutum (as Cycloum papillosum ). He
mentioned that they were surrounded by a thin wall, which
was obviously an introvert. He also observed larval release in
Alcyonidium polyoum (as Sarcochitum polyoum ).
Van Beneden ( 1844a ) described and illustrated testes, and
ovaries containing up to eighteen oocytes, inside the hermaphrodite zooids of the ctenostome Farrella repens (as
Laguncula ). He found an ovary on the body wall, whereas
the testis was observed on the funiculus, near its attachment
to the stomach. Maturing eggs were said at the time of disappearance of the nuclear membrane to be surrounded by the
“membrane externe vitelline ou le chorion” (p. 18). If this
membrane was a fertilization envelope, recorded in the late
ovarian oocytes of some Cheilostomata, then this should
point to intraovarian fertilization in Farrella . Interestingly,
Van Beneden, who believed that internal self-fertilization
occurred in Bryozoa, wondered if fertilization happened
before the egg left the “ovisac” [follicle]. He also observed
ovulated eggs as well as spermatozoids moving inside the
visceral coelom. Additionally, he found a special opening
[supraneural pore] near the base of the tentacles and described
release of eggs. In another paper ( 1844b ) Van Beneden
described and depicted a testis and motile sperm inside the
body cavity of Bowerbankia cf. imbricata (as B . densa ), and
sperm, eggs (both coelomic and isolated), an intrazooidal
embryo and settling larvae in Alcyonidium cf. hirsutum (as
Halodactyle vélu ). In addition, sperm aggregation in Flustra
foliacea and eggs (possibly still inside the ovary) in A. parasiticum (as Halodactyle parasite ) were illustrated.
Reid ( 1845 , p. 398) observed developing embryos inside
the “ovary-capsules” [ovicells] of the cheilostomes
Scrupocellaria reptans , S . scruposa (as Cellularia ), Bugula
avicularia (as C . avicularis ) and B. fl abellata (as Flustra
avicularis ), stating that ovicells were “fi lled with ovaries”. In
the latter species he described the ooecial vesicle and recorded
an increase in the thickness of its “membranous lining [that]
contained a number of nucleated cells”. This increase was
accompanied by “ovum” [embryo] enlargement and, obviously, was the fi rst observation of an embryophore [placental
analogue] in Bryozoa. Reid also observed larval release,
swimming and settlement in B. fl abellata . “Reddish brown
nucleated cells inclosed in a membrane (ova)” were described
in the broken zooids of Alcyonidium sp. (as A. parasiticum )
(p. 394).
Johnston ( 1847 , p. 262) expanded a review on bryozoan
sexual reproduction in the second edition of his monograph.
Based on the data of Grant ( 1827 ), Reid ( 1845 ) and Van
Beneden ( 1844a ), he stated that bryozoans are hermaphrodites whose eggs are formed “from the inner surface … of
the skin or coat which lines the interior of the cell” [epithelium of the body wall]. Further “the ovum falls, when mature,
into the space between it and the body of the polype; and in
this cavity, which is always full of a fl uid, probably seawater, it grows and appears to be rendered fruitful by admixture with the spermatozoa that are there prepared for this
union.”. At the same time, following general opinion (see
above), Johnston noted that in many genera eggs are formed
in the “calcareous capsules” [ovicells].
Dalyell ( 1848 ) observed developing embryos, and swimming and settling larvae in a few cheilostomes, among which
were Carbasea carbasea (as Flustra ), Flustra foliacea and
Securifl ustra securifrons (as Flustra truncata ). In
Bowerbankia imbricata (as B . densa ) he described and illustrated mature oocytes in the ovary and an embryo brooded in
the tentacle sheath of a zooid without a polypide.
Hancock ( 1850 , p. 193) observed an egg, surrounded by a
“delicate membranous sac” [ovary wall], at the site of the
funicular attachment to the cystid wall in the freshwater
ctenostome Paludicella (as P . procumbens ) (i.e. P . articuAppendices
“chorion” [fertilization envelope] in the brood chamber.
Nordmann also observed swimming larvae and mentioned
their settlement, followed by development of the ancestrula.
Johnston ( 1838 ) briefl y discussed the known facts on
bryozoan reproduction in the fi rst edition of his famous
monograph “A history of the British zoophytes”. He mainly
followed and widely cited the paper of Grant ( 1827 ), writing
that “the ova formed in the cells [zooids]” (p. 47).
Some observations of Farre ( 1837 ) were restated and
explained by Hincks ( 1851 ), who described the structure of
the ciliary intertentacular organ in the cheilostome Electra
pilosa (as Membranipora ) and recorded sperm release
through it. This is in contradiction with the more recent
observations of Silén ( 1966 ), who described sperm release
through the pores in the tips of the tentacles in two other species of Electra (see below). However, the description of
Hincks is so detailed and convincing that one can be left in
no doubt whether sperm expulsion may really be sometimes
possible through the intertentacular organ in E. pilosa . In
connection with this, Prouho ( 1892 ) suggested that this could
happen if the rest of the sperm [remaining after intrazooidal
self-fertilization] exited at the end of the reproductive period.
Hincks suggested that the intertentacular organ could also be
used for the release of eggs after their ovulation and fertilization in the body cavity, and this was later proven by Prouho
( 1889 ), who described egg liberation in the ctenostome
Alcyonidium albidum . Additionally, Hincks ( 1851 ) observed
sperm in Bowerbankia sp. and larval release in A . hirsutum
(as Cycloum papillosum ).
Kölliker ( 1841 ) recorded the presence of eggs and sperm
in Alcyonidium sp. (as A . gelatinosum ) and pointed out that
the “cercariae” of Farre were spermatozoids, which Kölliker
described, measured and precisely depicted. He believed that
the gonads were contained not inside the zooids, but between
them in the branches of the colony.
Hassall ( 1841 ) observed developing embryos, which he
called “ciliated eggs”, in groups of six or seven arranged in a
circle in Alcyonidium hirsutum (as Cycloum papillosum ). He
mentioned that they were surrounded by a thin wall, which
was obviously an introvert. He also observed larval release in
Alcyonidium polyoum (as Sarcochitum polyoum ).
Van Beneden ( 1844a ) described and illustrated testes, and
ovaries containing up to eighteen oocytes, inside the hermaphrodite zooids of the ctenostome Farrella repens (as
Laguncula ). He found an ovary on the body wall, whereas
the testis was observed on the funiculus, near its attachment
to the stomach. Maturing eggs were said at the time of disappearance of the nuclear membrane to be surrounded by the
“membrane externe vitelline ou le chorion” (p. 18). If this
membrane was a fertilization envelope, recorded in the late
ovarian oocytes of some Cheilostomata, then this should
point to intraovarian fertilization in Farrella . Interestingly,
Van Beneden, who believed that internal self-fertilization
occurred in Bryozoa, wondered if fertilization happened
before the egg left the “ovisac” [follicle]. He also observed
ovulated eggs as well as spermatozoids moving inside the
visceral coelom. Additionally, he found a special opening
[supraneural pore] near the base of the tentacles and described
release of eggs. In another paper ( 1844b ) Van Beneden
described and depicted a testis and motile sperm inside the
body cavity of Bowerbankia cf. imbricata (as B . densa ), and
sperm, eggs (both coelomic and isolated), an intrazooidal
embryo and settling larvae in Alcyonidium cf. hirsutum (as
Halodactyle vélu ). In addition, sperm aggregation in Flustra
foliacea and eggs (possibly still inside the ovary) in A. parasiticum (as Halodactyle parasite ) were illustrated.
Reid ( 1845 , p. 398) observed developing embryos inside
the “ovary-capsules” [ovicells] of the cheilostomes
Scrupocellaria reptans , S . scruposa (as Cellularia ), Bugula
avicularia (as C . avicularis ) and B. fl abellata (as Flustra
avicularis ), stating that ovicells were “fi lled with ovaries”. In
the latter species he described the ooecial vesicle and recorded
an increase in the thickness of its “membranous lining [that]
contained a number of nucleated cells”. This increase was
accompanied by “ovum” [embryo] enlargement and, obviously, was the fi rst observation of an embryophore [placental
analogue] in Bryozoa. Reid also observed larval release,
swimming and settlement in B. fl abellata . “Reddish brown
nucleated cells inclosed in a membrane (ova)” were described
in the broken zooids of Alcyonidium sp. (as A. parasiticum )
(p. 394).
Johnston ( 1847 , p. 262) expanded a review on bryozoan
sexual reproduction in the second edition of his monograph.
Based on the data of Grant ( 1827 ), Reid ( 1845 ) and Van
Beneden ( 1844a ), he stated that bryozoans are hermaphrodites whose eggs are formed “from the inner surface … of
the skin or coat which lines the interior of the cell” [epithelium of the body wall]. Further “the ovum falls, when mature,
into the space between it and the body of the polype; and in
this cavity, which is always full of a fl uid, probably seawater, it grows and appears to be rendered fruitful by admixture with the spermatozoa that are there prepared for this
union.”. At the same time, following general opinion (see
above), Johnston noted that in many genera eggs are formed
in the “calcareous capsules” [ovicells].
Dalyell ( 1848 ) observed developing embryos, and swimming and settling larvae in a few cheilostomes, among which
were Carbasea carbasea (as Flustra ), Flustra foliacea and
Securifl ustra securifrons (as Flustra truncata ). In
Bowerbankia imbricata (as B . densa ) he described and illustrated mature oocytes in the ovary and an embryo brooded in
the tentacle sheath of a zooid without a polypide.
Hancock ( 1850 , p. 193) observed an egg, surrounded by a
“delicate membranous sac” [ovary wall], at the site of the
funicular attachment to the cystid wall in the freshwater
ctenostome Paludicella (as P . procumbens ) (i.e. P . articuAppendices