File:Amphioxus Three stages in the segmentation of the ovum, according to the bilateral type.jpg

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Fig. 57. Three stages in the segmentation of the ovum, according to the bilateral type. From the lower pole. (After E. B. WILSON.)

A. Eight-cell stage. A, B, C, D. The four macromeres, above which are seen portions of the four micromeres.

I-I, Plane of first cleavage, with respect to which the cells divide in such a way as to become arranged in a bilaterally symmetrical manner.

II-II, Plane of second cleavage,

B. Transition to the sixteen-cell stage.

C. Sixteen-cell stage. The line in each cell indicates the direction in which the next division of the cell would take place.
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Source https://archive.org/details/cu31924001026131/page/108/mode/1up?view=theater Amphioxus and the ancestry of the vertebrates. New York, London, Macmillan.
Author Willey, Arthur

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current18:31, 24 March 2024Thumbnail for version as of 18:31, 24 March 20241,608 × 547 (313 KB)Rasbak (talk | contribs){{information |description=Fig. 57. Three stages in the segmentation of the ovum, according to the bilateral type. From the lower pole. (After E. B. WILSON.) A. Eight-cell stage. A, B, C, D. The four macromeres, above which are seen portions of the four micromeres. I-I, Plane of first cleavage, with respect to which the cells divide in such a way as to become arranged in a bilaterally symmetrical manner. II-II, Plane of second cleavage, B. Transition to the sixteen-cell stage. C. Sixteen...

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