Vol.LlI March, 1927 No. 3 BIOLOGICAL BULLETIN THE EFFECT OF LACK OF OXYGEN ON SEA URCHIN EGGS. ETHEL BROWNE HARVEY. It has long been known that fertilized sea urchin eggs may live for some time in the absence of oxygen without division, and divide on readmission of oxygen (Loeb, '95). Since the role of oxygen is of fundamental importance in the life of the cell, I thought it might be of interest to make a study of the changes that take place in individual eggs during lack of oxygen at different stages of development, with special reference to the mitotic figure. The opportunity to procure excellent material for this study was given at the Naples Laboratory, where the perfectly transparent eggs of Echinus microtuberculatus and Strongylocentrotus lividus may be procured during the entire year. It is with great pleasure that I thank Dr. Dohrn for his kindness and courtesy while working in the Stazione Zoologica, and also the Association to aid Seientific Research by Women for the use of their room. The observations were made on eggs in a hanging drop in a modified Engelmann's chamber to which pure hydrogen 1 was admitted. The eggs were entangled in threads of platinized asbestos to absorb the last traces of oxygen, and they were stained in methylene blue in order to tell when the oxygen was completely gone. Under the conditions of the experiment, it was found that it took about twenty minutes for the oxygen to be entirely used up as indicated by the colorless condition of the originally blue stained eggs. The eggs of Echinus micro-tuberculatus and Strongylocentrotus lividus gave practically the 1 The hydrogen was prepared in a Kipp generator from zinc and sulphuric acid washed with alkaline permanganate and passed over platinized asbestos heated to redness in a quartz tube. 11 147
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