Fig. 10 in Reproductive biology, embryonic development and matrotrophy in the phylactolaemate bryozoan Plumatella casmiana

Fig. 10 Semithin sections of the embryo sac of Plumatella casmiana. The border between the ectodermal and mesodermal layer of the embryo sac wall are shown by a dashed line in b–d. a Attachment site of the embryo sac to the body wall showing continuity of its layers with those of the body wall. b Embryo sac with prominent outer mesodermal and thin inner ectodermal layer of (separated by dashed line). Contact cells of blastula-staged embryo are in connection with the ectoderm and mesoderm of the embryo sac (arrowheads). c Longitudinal section showing a cavity lined by the distal maternal ectodermal cells. Contact cells are indicated by arrowhead. d Section of a blastula and its central cavity. Contact cells are apparent in the upper part of the embryo (arrowheads). The epi- thelial lining of the embryo in this region is thicker and indicates mesoderm formation. Abbreviations: b polypide bud, e embryo, ed epidermis (ectodermal origin), esm mesoderm of embryo sac, mec maternal ectoderm cells, ov ovary