NATUBAL DEATH AND FERTILIZATION 745 



stance is perhaps formed (for example, an acid) in the dying 

 eggs which brings about a single cleavage. 



The relations which exist between maturation and natural 

 death upon the one hand, and fertilization and prolongation 

 of life upon the other, lead us to the conclusion that a '"fer- 

 tilization" must perhaps come to pass in every egg, even in 

 those naturally parthenogenetic. Only, according to our 

 idea, the act of fertilization is not identical with the mor- 

 phological process which is designated fertilization. It is 

 rather a chemical or a physico-chemical act which accelerates 

 certain (synthetical?) metabolic changes in the egg, which 

 occur in the egg under ordinary conditions also, only much 

 too slowly, The difference between naturally partheno- 

 genetic eggs and the eggs which must be fertilized before 

 they can develop consists perhaps in this, that to the latter 

 the catalytically working substance or complexus of condi- 

 tions must be added from the outside in order to accelerate 

 the synthetical ( ?) processes, while in the naturally partheno- 

 genetic eggs these substances are formed within the eggs 

 (possibly in conjunction with the processes of maturation). 



The connection between the prolongation of life and fer- 

 tilization clearly points out that every purely morphological 

 theory of fertilization is incomplete and that a correct theory 

 of this process must have a physico-chemical basis. The 

 means of reaching this basis I see in further attempts at 

 causing development of unfertilized eggs through unequiv- 

 ocal physical and chemical means. 



VII. CONCLUSIONS 



1. Our observations and experiments seem to show that 

 in the same sea-water and under otherwise identical con- 

 ditions, mature but unfertilized starfish eggs soon die, while 

 immature as well as mature but fertilized eggs live longer. 



2. It seems certain that the rapid death of the mature 



