That dividing Arbacia eggs show periods of varying susceptibility and resistance when exposed to chemical substances and to various physical conditions has been proved by numerous investigations. When eggs from a single fertilized lot were placed at regular successive intervals after fertilization in cyanide containing sea-water (m/100 to m/200), Lyon found that they were highly resistant to poisoning fifteen or twenty minutes after fertilization, while eggs exposed to the same solution at the time of cytoplasmic division were promptly killed. Later, after the first division had been completed, the resistance to poisoning again returned, followed by a second susceptible period at the second cleavage. Loeb later noted that the unfertilized eggs show greater resistance to cyanide poisoning than the fertilized eggs, and Mathews indicated that in dividing eggs, the period of maximum susceptibility is ''immediately before and during segmentation," and that just after segmentation the egg becomes relatively highly resistant.
Proceedings of the Iowa Academy of Science
©1920 Iowa Academy of Science, Inc.
Baldwin, Francis Marsh
"Susceptible and Resistant Phases of the Dividing Sea-Urchin Egg when Subjected to Various Concentrations of Lipoid-Soluble Substances, Especially the Higher Alcohols,"
Proceedings of the Iowa Academy of Science, 27(1), 287-300.
Available at: https://scholarworks.uni.edu/pias/vol27/iss1/56