238 PROBLEMS OF FERTILIZATION 



hypothesis that fertilization causes this union to occur 

 in the egg, and hence, owing to such binding of the 

 agglutinating side chain of the fertilizin, no sperm 

 reaction is possible. 



It will be noted that no postulate is made concerning 

 the mechanism of action of fertilizin on the egg. It is 

 necessary that the substance be present within the cor- 

 tex of the egg; if it is once lost, fertilizing power goes 

 with it. It operates in the cortical changes of fertili- 

 zation, for such changes are absent if the substance be 

 removed; it is therefore necessary also, at least indi- 

 rectly and possibly directly (see p. 265), for the internal 

 changes. The suggestion that the fertilizin may act 

 as a catalyzer is perhaps supported to a certain extent 

 by Richards and Woodward's (1915) determination of 

 some enzyme analogies of this substance. The sugges- 

 tion is in any event a natural one, as is shown by the 

 rather numerous suggestions in the literature concern- 

 ing the connection between activation and enzyme 

 action. 



Miss Woodward (1918) agrees that fertilizin is ne- 

 cessary for fertilization: eggs of Aster 'las and Arbacia, 

 from which it has been washed, will not fertilize, but 

 if secretion (fertilizin) be added to such eggs before 

 insemination they will fertilize. The latter observa- 

 tion outruns the determination of the present writer 

 and obviously constitutes a very critical point. The 

 dual nature of fertilizin is shown by its action in agglu- 

 tinating spermatozoa and by the production of parthe- 

 nogenesis in eggs of the same species when concentrated 

 on them. Such autoparthenogenesis was first described 

 by Glaser (1914^). The writer is not convinced that 



