I6 E. E. JUST. 



chanism of fertilization. Without going into details it may be 

 said that in Arbacia it is found that the egg secretes a substance, 

 fertilizin, whose presence is capable of quantitative determination 

 and which is necessary for fertilization since first, eggs washed 

 free of it are no longer capable for fertilization; second, fertilized 

 eggs no longer secrete it; and third, eggs after membrane forma- 

 tion with butyric acid are not capable of fertilization and do not 

 give off the substance. The perivisceral fluid of Arbacia, 

 moreover, produces an inhibiting effect on fertilization preventing 

 the action of fertilizin on the egg. 



My results with warming Nereis eggs parallel to a striking 

 degree these facts brought out in the studies of fertilization in 

 Nereis and Arbacia (Lillie, '12, '13a, '136, '14). Eggs washed 

 free of the bulk of fertilizin will not develop however long the 

 warming treatment lasts ; serum inhibits the artificial initiation of 

 developmental processes ; only the dry eggs with their full content 

 of fertilizin when suddenly shocked with elevation of temperature 

 respond with jelly formation and cleavage. It would seem, there- 

 fore, as I have suggested for Platynereis, that fertilizin is just as 

 essential for artificial initiation as for normal fertilization. The 

 difference seems to be that for artificial initiation more fertilizin 

 is required. Further attempts at Woods Hole this summer to 

 induce artificial parthenogenesis in Platynereis strengthen this 

 belief; a percentage of Platynereis eggs will fertilize in small 

 quantities of sea-water; the same bulk of eggs in the same 

 amount of water fail to respond when subjected to warming. 



If, therefore, as Loeb ('12a) says, "fertilization is primarily 

 and essentially artificial parthenogenesis"; or if "a theory of 

 fertilization must also be a theory of parthenogenesis at least 

 for the phenomena common to both"; and if "similarly a theory 

 of fertilization must be consistent with the facts of parthenogen- 

 esis" as Lillie ('14) suggests; these experiments, we are forced to 

 conclude, make another link in the chain of evidence which 

 supports the theory that fertilization is essentially a process of 

 the egg. The spermatozoon initiates the development of the 

 egg, as does warming, through the activation and the binding of 

 the fertilizin. 



