Studies on the Temnocephaloidea.–II. The Embryology of Caridi-nicola indica
*Communicated by Prof, E. W. MacBride, M.A., D.Sc., F.R.S., F.Z.S,
- 1Segmentation is irregular, and results in a syncytial blastoderm in which are found micronuclei and macronuclei.
- 2The micronuclei represent ectoderm, the macronuclei the endoderm.
- 3The endodermal nuclei are situated more posteriorly.
- 4A cavity appears in the endodermal mass. It is the endocœle which becomes very large.
- 5The other endodermal cells arrange themselves at the sides of the endocœle, and a few remain ventral to it.
- 6Three regions are differentiated in the ectodermal mass–an anterior group forms the brain and nerves; a middle group gives rise to the pharynx; and a posterior group, which lies ventral to the endocœle and gives rise to muscles, the parenchyma, and the outer ectodermal epithelium.
- 7The endocœle divides into two–a posterior part disappears among the yolk-mass, while the anterior past unites with the pharynx and opens into it.
- 8The alimentary canal consists of a pharynx, œsophagus, and intestine.
- 9The pharynx differentiates from the middle ectodermal mass; the cesophagus is the persistent anterior section of the endocœle; the intestine develops from cells proliferated from the posterior wall of the œophagus (persistent section of endocœle).
- 10The endoccele is homologous with the archenteron of other animals.
- 11The germariurn is differentiated from the median, ventral endodermal mass, the testes from the lateral endodermal masses; the genital ducts are formed partly of ectoderm and partly of endoderm.