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Studies on the Temnocephaloidea.–II. The Embryology of Caridi-nicola indica

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  • *Communicated by Prof, E. W. MacBride, M.A., D.Sc., F.R.S., F.Z.S,

Summary.

  • 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.
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