ON THE DEVELOPMENT OF THE SPONTANEOUSLY PARTHENOGENETIC EGGS OF ASTERINA (PATIRIA) MINIATA

Abstract

While engaged in a series of experiments on echinoderm hy bridology, @which,I was conducting. during the months of April and May, 1920, at Pacific Grove, California, I was forcibly struck •? by the frequency with which spontaneous parthenogenesis occurs in the starfish, Asterina (Patina) ntinata. When I use the term “? spontaneous,― I mean that eggs were in no way treated either •? by physical or by chemical agents. Precautions were taken, moreover, to prevent aA§cidCnth@l fertilization. The procedure was as follows: Sea water, brought in from the open sea and therefore free from the chemical ir@ipurities pres@ent in sea water that has been pumped through metal pipes, was allowed to stand at least four •? days at laboratory temperatures, .which during the month of May ranged from i6° to 19°C. It is certain that no sperms could •? live for this length of time in sea water. This method is chosen in preference to Loeb's practise of heating the sea water to @O C. for some time, because it involves no possil)le chemical changes in the sea water nor any driving out of oxygen. Before opening a starfish, it was scrubbed thoroughly in cold running fresh water and rinsed in a strong stream of fresh water. In case the animal proved to be a male it was discarded, and hands and instruments were scrubbed in fresh water before touching another starfish. If the animal proved to be a ripe female the ovaries were gently shaken into a finger-bowl containing 150 c.c. of the sea water prepared for the purpose and the bowl was cov ered with a clean glass plate and placed upon a table out of reach