28 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



All these observations point to the conclusion that the 

 processes determining or underlying nuclear division depend 

 upon oxidations. 



The eggs of the starfish must be fertilized at the time the 

 second polar body is given off or immediately afterward, since 

 otherwise they disintegrate and cannot be fertilized at alL 

 When we compare the rate of oxidations in starfish eggs imme- 

 diately before and after fertilization, we find no difference, as 

 Table I shows. It should be remarked that while as a rule 100 

 per cent of the sea-urchin eggs can be fertilized by sperm, in the 

 case of starfish eggs a much smaller percentage is usually ferti- 

 lized since in most cases not all the eggs become mature 

 simultaneously. 



TABLE I 1 



It is obvious that no noticeable increase in the rate of the 

 oxidation is caused in this egg through the entrance of the 

 spermatozoon. This is intelligible from the fact that those 

 oxidations which lead to nuclear division were already going on 

 in the eggs at the time the spermatozoon entered. 



3. Warburg 2 compared the rates of oxidations in the eight- 

 cell stage and the thirty-two-cell stage. Their ratio was as 

 4- 2 to 6-8; a slight increase. Wasteneys and I 3 measured 

 the change in the rate of oxidations each hour for five consecu- 

 tive hours after fertilization in the eggs of Arbacia at Woods 



1 Loeb and Wasteneys, Archiv f. Entwicklungsmechanik, XXXV. 556, 1912^ 



2 Warburg, Zeitschr. /. physiol. Chem., LVII, 1, 1908. 



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



