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Fig. 2.25 Schematic longitudinal sections of: ( A ) immersed cleithral
ovicell in Crassimarginatella sp. ( arrow indicates communication pore
plugged by non- specialized epithelial cells); ( B ) internal brood sac with
vestigial ooecium in Cauloramphus spinifer ( larger arrow indicates a
common opening leading to vestibulum and entrance to brood sac;
smaller arrow indicates ooecial communication pore plugged by a
pore-cell complex) (( A ) – From Ostrovsky et al. 2009a , courtesy of
Springer Verlag, http://link.springer.com/article/10.1007/s00435-0080070-8 ; ( B ) – From Ostrovsky et al. 2007 , courtesy of Zoological
Society of Japan, http://www.bioone.org/doi/abs/10.2108/zsj.24.1187
?journalCode=jzoo ). Abbreviations: bsw brood-sac wall, bw basal
wall, cr cryptocyst, dz distal zooid, ес ectooecium, en entooecium, fm
membranous frontal wall, m muscle strands of ooecial vesicle and
brood sac, mz maternal zooid, oc ooecial coelom, oe kenozooidal ooecium, of ovicell fl oor, op operculum, sc sclerite of ooecial vesicle, tw
transverse wall
2 Cheilostome Brood Chambers: Structure, Formation, Evolution