740 STUDIES IN GENERAL 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 PROLONGATION 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 larve 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 larvee 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 as 
long-lived larve 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- 
Digitized by Microsoft® 
