740 STUDIES IN GENEEAL PHYSIOLOGY 



those made by Harper upon pigeons must yet be made upon 

 mammals. Yet there seems to be no doubt that the mam- 

 malian egg of many species is also fertilized before it reaches 

 the uterus. Cases of extra-uterine pregnancy also point to 

 the possibility that fertilization may occur at the surface of 

 the ovary. 



VI. THE PEOLONGATION OF LIFE AND THE THEORY OF 

 FERTILIZATION 



Our experiments seem to have proved that the mature 

 unfertilized starfish egg dies within a few hours through 

 internal changes, but that the process of fertilization saves 

 the life of the egg. This is true, not only of the fertiliza- 

 tion of the starfish egg by spermatozoa, but also for the 

 chemical fertilization through hydrogen ions. Mr. Neilson 

 succeeded this year in keeping the parthenogenetic larvae of 

 starfish alive much longer than has thus far been the case 

 (over thirty days), and Dr. Fischer was able to accomplish 

 the same for the larvae produced osmotically from unfertil- 

 ized sea-urchin eggs. It is therefore possible that the chemi- 

 cal or osmotic fertilization of these eggs can give rise to aa 

 long-lived larvae as the fertilization of the egg through 

 sperm. 



But how does the spermatozoon, or the physical and 

 chemical means substituted for it, save the life of the egg, 

 and why does the mature egg die when it is not fertilized 

 by sperm or artificial means ? I believe that the answer 

 lies in this, that the fertilizing agencies accelerate metabolic 

 processes in the egg which, before fertilization, went on only 

 slowly. After fertilization by sperm or by the chemical or 

 physical means substituted for it, the egg divides and grows 

 which it did not do before fertilization occurred. Growth 

 is inconceivable without a preponderance of synthetical over 

 hydrolytical processes. I believe it possible that the deter- 



