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Fig. 4. Schematic diagrams to indicate the effect of yolk on the first cleavage division

Figure 4 shows diagrammatically the manner in which the first cleavage division is carried out in three types of eggs having different relative amounts and different distributions of yolk and protoplasm. In the egg of Amphioxus the yolk is relatively meager in amount and fairly uniformly distributed throughout the cell. An ovum with such a yolk distribution is termed isolecithal (homolecithal). An isolecithal egg undergoes a type of cleavage which is essentially an unmodified mitosis. The yolk is not sufficient in amount, nor sufficiently localized to alter the usual mode of cell division.

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Patten BM. The Early Embryology of the Chick. (1920) Philadelphia: P. Blakiston's Son and Co.

Cite this page: Hill, M.A. (2019, July 19) Embryology Patten004.jpg. Retrieved from

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© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G

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current15:46, 14 January 2011Thumbnail for version as of 15:46, 14 January 2011896 × 553 (116 KB)S8600021 (talk | contribs)==Fig. 4. Schematic diagrams to indicate the effect of yolk on the first cleavage division== {{Template:Patten_1920_Figures}}
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