FERTILIZATION ON PARTHENOGENESIS. 139 



i. e., by the activation of this substance, within the egg. If this 

 activation by parthenogenetic agents is rendered complete we 

 should naturally expect the egg to acquire essentially the same 

 condition as it does following the act of fertilization. If fer- 

 tilization depends upon the activation of fertilizin and this has 

 been once activated by artificial agents' we should expect fertiliza- 

 tion to be just as impossible as in a normally fertilized egg. 

 Experiments lead us to believe that fertilization is a complex 

 series of reactions which if once completed exclude all possi- 

 bilities of repetition. 



According to Loeb ('13, page 225) fertilization depends upon 

 the introduction of two separate and distinct sperm-borne 

 substances a lysin-like substance and a substance producing 

 the so-called corrective effect. The former is thought of as 

 exercising a cytolytic influence upon the cortex of the egg that 

 results in the production of a membrane: unless the influence of 

 this lysin-like substance is counteracted in some way the proc- 

 esses initiated by it continue until the egg is totally destroyed. 

 This substance acts before penetration of the sperm and is not 

 specific, as shown by the fact that starfish sperm so act upon 

 sea urchin eggs that they cause membrane production and sub- 

 sequent destruction of the egg unless this is prevented by a 

 secondary corrective agent. The latter substance according to 

 Loeb acts only after the spermatozoon enters the egg; it stops the 

 cytolytic action of the first substance and permits the egg to 

 develop normally. 



Loeb ('14 and '15) has objected to the fertilizin hypothesis 

 on grounds which if correct, would go a long way toward sealing 

 the fate of that hypothesis. Loeb's contentions in brief are 

 these: 



1. He maintains that this agglutinative substance is not a 

 secretion from the egg but is derived from the clear transparent 

 layer of jelly surrounding the egg, the so-called "chorion layer." 

 If the jelly layer is destroyed no more fertilizin is present. Lillie 

 ('14 and 'i5a) however has shown that this is not so. 



2. He further asserts that eggs that have produced membranes 

 as a result of butyric acid treatment or other parthenogenetic 

 agents undergo not only further development but entirely normal 



