From Embryology

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Fig. 16. Fertilization of the eggs of the star-fish and sea-urchin

  • A, B, C - entrance of the sperm into the cytoplasm (star-fish)
  • D - mature spermatozoon of the sea-urchin
  • E-H - successive stages in the penetration of the sperm nucleus (♂N) and centrosome (♂C) into the cytoplasm
  • I-L - stages in the approach of the sperm nucleus (♂N) to the egg nucleus (♀N), the division of the sperm centrosome (♂O) and the first cleavage spindle.

Fol, Wilson, from Conklin Heredity and Environment.

Links: sea urchin

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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)


Bailey FR. and Miller AM. Text-Book of Embryology (1921) New York: William Wood and Co.

Cite this page: Hill, M.A. (2024, April 12) Embryology Bailey016.jpg. Retrieved from

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