File:Echinoidea cleaving egg.jpg
Summary
| 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. |
| Date | |
| 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. |
Licensing
 |
This work is in the public domain in its country of origin and other countries and areas where the copyright term is the author's life plus 70 years or fewer. Category:PD-old missing SDC copyright status You must also include a United States public domain tag to indicate why this work is in the public domain in the United States.Category:PD-old missing SDC copyright status |
| This file has been identified as being free of known restrictions under copyright law, including all related and neighboring rights. | |
Category:CC-PD-Mark Category:PD OldCategory:PD-old missing SDC copyright status
 |
This file, which was originally posted to an external website, has not yet been reviewed by an administrator or reviewer to confirm that the above license is valid. See Category:License review needed for further instructions. |