Fig. 7 in Reproductive biology, embryonic development and matrotrophy in the phylactolaemate bryozoan Plumatella casmiana

Fig. 7 Contact areas of embryos of Plumatella casmiana and the maternal ectoderm. Semithin sections. The border between the ectodermal and mesodermal layer of the embryo sac are shown by the dashed line in a–c. a Blastula stage in a bilayered embryo sac. The latter consists of a thick (outer) mesoderm and a thin inner lining of maternal ectoderm. One blastomere of the embryo is in contact (arrow) with the adjacent ectodermal cell of the embryo sac. The cytoplasm of the connected maternal ectoderm cell stains less intense than adjoining cells. b Detail of the embryo sac with a maternal ectodermal cell (arrow) in contact with the blastomere. c Detail of a blastula showing contact of a blastomere with the maternal ectoderm in the proximal area of the embryo sac. d Late embryo showing several ectodermal cells at the posterior pole of the embryo forming contact with the remaining maternal ectodermal cells (arrow). Abbreviations: e embryo, ebs embryo sac, eme embryonic ectoderm, emm embryonic mesoderm, mec maternal ectoderm cells, ov ovary