PRESERVATION OF THE LIFE OF THE EGG 289 



mature egg, while fertilization, which makes the egg immortal, 

 raises the rate of oxidations considerably, at least in the egg 

 of the sea-urchin. We have seen that in the unfertilized egg of 

 the sea-urchin oxidations take place though at a slow rate. 

 The unfertilized eggs seem to perish very rapidly through 

 these oxidations. We have stated that the mature unfertilized 

 egg resembles an anaerobe, while the act of fertilization trans- 

 forms it into an aerobe. We are certainly here confronted 

 with one of the most interesting and far-reaching features of 

 the problem of fertilization. The unfertilized egg is perhaps 

 at present the only instance of a cell for which " natural death ' : 

 can be proven. The act of fertilization or rather the induce- 

 ment of development procures theoretical immortality for the 

 egg, since the sex cells of the new individual to which the egg 

 gives rise are parts of the egg. 



The oxidations are, however, not the only processes which 

 are responsible for the premature ''natural death " of the 

 unfertilized egg; otherwise it should be possible to keep it 

 alive indefinitely without oxygen, which is not the case. The 

 act of fertilization brings about a profound physicochemical 

 modification in the egg which is not confined to one type of 

 chemical reactions. 



