26 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



At this temperature the velocity of the chemical reactions in 

 the egg is reduced almost to zero. On raising the temperature 

 again, no division of the fertilized egg takes place in the hydro- 

 gen atmosphere; but on allowing air to enter the receptacle, the 

 processes of nuclear and cell divisions are again at once resumed. 

 Perhaps it can be still more strikingly demonstrated that oxida- 

 tion is necessary for the development of the egg, by suppressing 

 the oxidation processes by certain poisons. It has long been 

 known that oxidations in the cell can be prevented by the addi- 

 tion of a little potassium cyanide, even when oxygen is present. 

 I have found that the addition of 0.5 c.c. of a 1/20 per cent 

 KCN solution to 50 c.c. of sea-water is sufficient to stop almost 

 immediately the effect of the spermatozoon in the fertilized 

 sea-urchin egg. When, however, such an egg has been trans- 

 ferred to normal sea-water and good aeration has been estab- 

 lished, its development proceeds normally, provided that the 

 eggs have not remained too long in the potassium cyanide 

 solution. 



From these facts the writer came to the conclusion that one 

 essential effect of the entrance of the spermatozoon into the egg 

 of the sea-urchin is the acceleration of processes of oxidation. 1 

 Oxidations go on also in the unfertilized egg. He concluded 

 this from the fact that the unfertilized eggs in general disin- 

 tegrate in a comparatively short time, while the addition of 

 KCN or the withdrawal of oxygen prevented this disintegration, 2 

 and he explained this phenomenon on the assumption that the 

 oxidations in the unfertilized eggs accelerated their disintegra- 

 tion. The correctness of these ideas has since been proved by 

 direct measurements. 



O. Warburg was the first to measure the consumption of 

 oxygen in the unfertilized and fertilized sea-urchin egg, Arbacia 



1 Loeb, "Ueber den chemischen Charakter des Befruchtungsvorgangs," 

 Biochem. Zeitschr., I, 183, 1906, and also preface to Untersuchungen ueber kunstliche 

 Parthenogenese, Leipzig, 1906. 



2 Loeb, Pfliiger's Archiv, XCIII, 59, 1902. 



