FERTILIZATION AND OXIDATION 2V 



pustulosa, at Naples, by Winkler's method, and found that after 

 fertilization the egg consumes from six to seven times as much 

 oxygen as before fertilization. 1 Wastene}^ and I determined 

 the consumption of oxygen in unfertilized eggs of Arbacia 

 at Woods Hole. We found that immediately after fertili- 

 zation the egg consumes almost four times as much oxygen 

 as before fertilization. 2 In experiments on Strongylocentrotus 

 purpuratus in Pacific Grove we found that immediately after 

 fertilization the egg consumed five to seven times as much 

 oxygen as before fertilization. 3 



This difference in the rate of oxidations in the unfertilized 

 and fertilized eggs of the sea-urchin is probably due to the fact 

 that the unfertilized egg of the sea-urchin is usually in the 

 resting stage, i.e., no nuclear divisions are going on in it, 

 when it is taken out of the ovary and it generally remains in 

 this state if no spermatozoon enters. 



2. The conditions are, however, entirely different in the 

 starfish egg. This egg is, as a rule, immature when taken out 

 of the ovary, but as soon as it gets into the sea-water, it 

 may become mature; i.e., two nuclear divisions take place in 

 succession and the polar bodies are thrown out. I have shown 

 in a former paper that this process requires the presence of free 

 oxygen in the same way as the developing sea-urchin egg. Lack 

 of oxygen or presence of KCN prevents these nuclear maturation 

 divisions in the starfish egg with the same certainty as it does 

 the nuclear divisions in the fertilized sea-urchin egg. 4 And, 

 moreover, I was able to show that a slightly alkaline reaction 

 of the surrounding solution is as favorable to the process of 

 maturation of the starfish egg as it is to the segmentation of 

 the fertilized egg of Strongylocentrotus purpuratus. 



1 O. Warburg, Zeitschr. f. physiol. Chem., LVII, 6, 1908. 



- Loeb and Wasteneys, Biochem. Zeitschr., XXXVI, 351, 1911. 



3 Loeb and Wasteneys, Jour. Biol. Chem., XIV, 469, 1913. 



< Loeb, "Maturation, Natural Death and the Prolongation of the Life of 

 Unfertilized Starfish Eggs," Biol. Bull., Ill, 295, 1902. 



