306 LOEB. 



or accelerated the egg dies. The wasting of the body in old age 

 also indicates a decrease in synthetical processes. Whether the 

 second critical period occurring in old age is similar to the critical 

 period of the egg cannot yet be determined. Yet it is not impos- 

 sible that the question of the prolongation of life at this period 

 should pass over into the question of the possibility of accelerating 

 synthetical processes. 



We, therefore, come to the conclusion that fertilization 

 accelerates a series of chemical changes (syntheses?) in the 

 egg which do not occur sufficiently rapidly without spermatic, 

 chemical or osmotic fertilization in the eggs of the majority of 

 animals. But why does the mature egg die when these processes 

 are not accelerated, and why does it remain alive before it 

 maturates? The egg must often exist for years in the immature 

 condition in the ovary. In answer I can only suggest that the 

 processes underlying maturation are at least in some form of a 

 destructive nature (one might think of antolytic processes) which 

 the egg cannot withstand for an indefinite length of time without 

 dying. In many eggs the velocity of these destructive (autolytic?) 

 processes may be greater than in others and this may determine 

 the differences in the velocity with which the mature, unfertilized 

 egg dies. It is in harmony with this view that when maturation 

 is prevented, or the mature egg is put under condition which 

 inhibit the process of maturation or the chemical processes under- 

 lying it, that the life of the egg is lengthened. Lack of oxygen 

 or the addition of an acid work in this way in the case of starfish 

 eggs ; a slight addition of potassium cyanide in the case of starfish 

 and sea-urchin eggs. But since all of these substances injure the 

 eggs indirectly and do not entirely do away with the destructive 

 (autolytic?) processes occurring within the egg, life is not pro- 

 longed to the same extent by these means as by fertilization in 

 which case life is prolonged not only through an inhibition of the 

 destructive but also through an acceleration of the ' synthetical 

 processes. 



That the chemical processes which underlie maturation are not 

 identical with those which bring about fertilization seems to be 

 supported by the observation made above, that the same means 

 the treatment with acid which causes the mature egg to 



