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File:Echinoidea cleaving egg.jpg

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Description Fig. 163. Developmental potencies (cell lineage) of isolated blastomeres of the cleaving sea-urchin egg. representing different levels along the egg axis (from Huxley and DeBeer, '34, after Horstadius). Observe the following: (1) Progressing from the animal pole to the vegetative pole, the potency for developing the sensory cilia decreases from animal pole cells I to animal pole cells II. (2) The potency for developing motile cilia increases from animal pole cell II to vegetative pole cell I. (3) The potency for gastrulation becomes greater from vegetative pole cell I to vegetative pole cell II. (4) In the development of vegetative pole cell I, shown at the right of vegetative I, if the third (equatorial) cleavage plane happens to be displaced near the animal pole, an isolated vegetative cell I has more animal pole potencies and will develop apical cilia; if the cleavage plane is displaced toward the vegetative pole, the vegetative pole cell I will attempt to gastrulate. (5) The disc of vegetative cells II plus the micromeres produce a gut so large it will not invaginate and hence forms an exogastrula.
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Source https://archive.org/details/comparativeembry00nels/page/327/mode/1up?view=theater&q=BLASTULATION+ Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illustrations.
Author Nelsen, Olin E.

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current18:08, 11 March 2024Thumbnail for version as of 18:08, 11 March 20241,109 × 1,483 (1.05 MB)Rasbak (talk | contribs){{Information |description=Fig. 163. Developmental potencies (cell lineage) of isolated blastomeres of the cleaving sea-urchin egg. representing different levels along the egg axis (from Huxley and DeBeer, '34, after Horstadius). Observe the following: (1) Progressing from the animal pole to the vegetative pole, the potency for developing the sensory cilia decreases from animal pole cells I to animal pole cells II. (2) The potency for developing motile cilia increases from animal pole cell II...

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