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8. Notes on some early Blastocysts of the South American Bat Molossus
Author(s) -
Sansom G. S.
Publication year - 1932
Publication title -
proceedings of the zoological society of london
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0370-2774
DOI - 10.1111/j.1469-7998.1932.tb06205.x
Subject(s) - ectoderm , trophoblast , blastocyst , anatomy , inner cell mass , biology , chemistry , microbiology and biotechnology , embryo , embryogenesis , fetus , placenta , pregnancy , genetics
S ummary . The early development of Molossus agrees fairly closely with that of the other Micro‐Cheiroptera, as described by Keibel, da Costa, and Levi. The orientation of the blastocyst at right angles to the mesometrial axis is noteworthy; it occurs in all the six early states, but is not preserved in the last, considerably later blastocyst, where the embryonal disc is directed more towards the antimesometrial side. In Pl. II. fig. 7 an arrow indicates the direction of the mesometrium, and it will be seen that the greater part of the ectodermal plate lies in a plane at about 40d̀ to the mesometrial axis. The primitive amniotic cavity arises as a cloft or clefts in the amnioectodermal mass, and its formation is apparently initiated by the rearrangement of the cells. The roof of this cavity thins out and ultimately disappears, with the result that a cavity is formed bounded on the one side by the shielf ectoderm and on the other by the thin layer of covering trophoblast. According to Levi, the definitive amniotic cavity is formed by the ingrowth of ectoderm, from the margins of the ectodermal shield, in contact with the covering trophoblast. There are indications in Ol. II. fig. 8 that this process has already started. The slight activity of the eyto‐trophoblast and the apparent absence of syneytio‐trophoblast, even in the latest stage herein described, are noteworthy. The trophoblast in these early stages appears to be devoid of phagocytic or eytolytic properties.