Ill 



FERTILIZATION AND OXIDATION 



1. Eighteen years ago the writer showed that if freshly 

 fertilized animal eggs (of sea-urchins and fishes) are deprived 

 of all oxygen, no nuclear or cell division is possible.^ Godlew- 

 ski^ and Samassa' have found the same with frog eggs, and 

 since then I have convinced myself that it holds for the eggs 

 of the starfish, annelids, molluscs, and probably generally. In 

 the same way oxygen is necessary for the maturation of the egg. 



In these experiments on the prevention of development of 

 the egg by lack of oxygen, one must guard against a source 

 of error which lies in the fact that some time must elapse before 

 the air or oxygen has been driven out of the dish containing the 

 egg. Since in many forms the first division of the nucleus 

 takes place in a little less than an hour, if the temperature is 

 high enough, and since it often requires as long, or even a longer 

 period, to replace all the oxygen by hydrogen, it may easily 

 happen that a nuclear, or even a cell division, may take place 

 after the egg has been placed in the stream of hydrogen.* I 

 avoided this source of error by cooling with ice the vessel con- 

 taining the eggs to 0° for as long as appeared necessary from the 

 foregoing experiments to replace all the oxygen by hydrogen. 



1 Loeb, "Die physlologische Wirkung des Sauerstofl-mangels," PflUger's Archiv, 

 LXII, 249, 1895. 



2 Godlewskl, " Die Einwirlcung des Sauerstolls auf die EntwicMung von Bono, 

 etc.," Archiv f. Entwichlungsmechanik, XI, 585, 1901. 



3 Samassa, Verhandl. d. naturh.-med. Vereins zu Heidelberg, IV, 1898, and Ver- 

 handl. d. deutach. Zool. Oeaellsch., 1896 (quoted from Godlewski). 



* It miist not be taken for granted in general that oxygen is unimportant, if 

 tlie experimenter does not succeed in suppressing all signs of life after a short pas- 

 sage of hydrogen or nitrogen through a vessel. It must not be forgotten that it 

 takes a long time before the last trace of oxygen is driven out, and that often a 

 trace of oxygen is quite sufficient to render possible the life phenomenon under 

 Investigation. 



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