INITIATION OF DEVELOPMENT IN EGG OF ARBACIA. 42! 



III. 



Blood blocks fertilization in the egg of Arbacia. Lillie's ex- 

 periments show this. The findings reported above but confirm his. 



If we inquire as to the mode in which blood blocks fertilization, 

 we must recall the role of fertilizin in the fertilization-reaction. 

 That the fertilizability of the egg depends upon the presence of 

 fertilizin, the following facts show: Immature eggs, fertilized eggs, 

 and eggs with butyric acid membranes do not secrete fertilizin. 

 They are also incapable of fertilization. Fertilizable eggs washed 

 free of fertilizin lose their capacity for fertilization. But the 

 failure of eggs in the presence of blood does not place these eggs 

 in the same category with fertilizin-f ree eggs. 



The failure of eggs in blood to fertilize is not due to the blocking 

 of the reaction between sperm and fertilizin. It will be recalled 

 that the presence of fertilizin in sea-water is indicated by its 

 agglutinative action on specific sperm. This action is not lost in 

 the presence of blood. ' It can not be supposed," says Lillie, " that 

 the plasma operates by preventing the adhesion of the sperma- 

 tozoon to the egg if this is brought about by agglutination, because 

 it was found that the agglutination of spermatozoa by means of 

 egg secretions takes place as readily in the plasma as in sea- water ' 

 (Lillie, '19, page 175). The action of blood is thus on the fer- 

 tilizin ; it constitutes a block between fertilizin and the egg itself. 

 Since eggs of Arbacia inseminated in blood are found with sperm 

 attached to or within the cortex, it must be concluded that Lillie's 

 interpretation of the inhibitory action of blood is sustained. 



Finally, Lillie's copper experiments ('21 ) reveal the latent period 

 in the fertilization reaction. If it prove that blood acts similarly, 

 we may have an additional method for study of the latent period. 

 We may thus be able more closely to approach an understanding 

 of the fertilization-reaction. 



LITERATURE. 

 Lillie, Frank R. 



'14 Studies of Fertilization, VI. The Mechanism of Fertilization in Ar- 

 bacia. Jour. Rxp. Zool., Vol. 16, pp. 523590. 



'19 Problems of Fertilization. The University of Chicago Press, xii + 278 

 PP. 



