The development of the human body : a manual of human embryology / by J. Playfair McMurrich.

  • McMurrich J. Playfair (James Playfair), 1859-1939.
Date:
1910
Catalogue details

Licence: In copyright

Credit: The development of the human body : a manual of human embryology / by J. Playfair McMurrich. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    Amphioxus (Fig. 16), but one of the tiers of cells of the eight-celled stage is very much smaller than the other (Fig., 17, B). In the subsequent stages of segmentation the small cells of the upper pole divide more rapidly than the larger ones of the lower pole, the activity of the latter seeming to be retarded by the accumulation of the yolk, and the result- Fig. ]7.~Stages in the Segmentation of Amblystoma.—(Eyclcs~ hymer.) ing blastula (Fig. 17, D) shows a very decided difference in the size of the cells of the two poles. In the ova of reptiles and birds the amount of yolk stored up in the ovum is very much greater even than in the am- phibia, and it is aggregated at one pole of the ovum of which it forms the principal mass, the yolkless protoplasm appearing as a small disk upon the surface of a relatively 5