FERTILIZATION-REACTION IN ECHINARACHNIUS PARMA. 303 



but the eggs of Asterias show practically no difference before 

 and after fertilisation. These results indicate that permeability 

 changes, like those of oxidation, are indicia of cell division. 



Finally, Mathews has studied the effect of KCN on fertilized 

 Asterias and Arbacia eggs. His findings on Arbacia confirm the 

 earlier observations of Lyon on this egg. Mathews finds that 

 the susceptibility of the starfish egg to KCN coincides with the 

 development of the asters, while the period of immunity coin- 

 cides with the retrogression of the asters. There is thus a rhythm 

 of alternate increase and decrease of susceptibility to KCN which 

 accompanies the rhythm of the mitotic process. The suscep- 

 tibility to cyanide is, therefore, comparable to the rhythm of 

 viscosity changes and to that of permeability. 



With Asterias eggs, however, Mathews got unsatisfactory re- 

 sults. He could not discover in this egg the sharp periods of sus- 

 ceptibility to KCN discovered in the Arbacia egg. I venture the 

 opinion that this result is due to the fact that in Asterias* the 

 maturation division is in process at the time of insemination. It 

 would, therefore, be difficult if not impossible to obtain in the 

 Asterias egg just after insemination a stage comparable to that 

 in the Arbacia egg just after insemination. Indeed, at no time 

 after insemination until the appearance of the cleavage asters 

 could a fair comparison between these eggs be made. 



In brief, these changes of viscosity, oxidation, permeability, 

 and susceptibility to KCN are not changes incident to the fer- 

 tilization-reaction per se; they are changes that are bound up 

 with the problem of cell division. They are, therefore, in no wise 

 peculiar to the fertilized egg. They cannot be regarded as ex- 

 plaining the activation of the egg. 



C. The Fertilizin Theory of Lillie. 



At present the best working hypothesis for the study of the 

 fertilization-reaction is the fertilizin theory of Lillie. The fer- 

 tilizin theory postulates that development is initiated through 

 the ovogenous substance, fertilizin. The sperm activates the 

 fertilizin and this reaction between sperm and fertilizin is the 

 first step in the developmental processes in the egg. The acti- 

 vated fertilizin acts on both egg and sperm. 



