274 LIBBIE H. HYMAN. 



transmitted changes recorded in this paper are: the roughening 

 (gelation) of the egg and the elevation of the fertilization mem- 

 brane. To these may be added those recorded by Just ('19, '22) 

 the loss by the egg of fertilizibility, the passage of materials from 

 the cortex into the perivitelline space, and the softening of the 

 vitelline membrane. 



The problem of the activation of the egg becomes thus a 

 problem of the nature of stimulation in general and cannot be 

 solved until the more general problem has attained solution. 



8. Summary. (a) The eggs used were those of Strongylo- 

 centrotus franciscanus and purpuratus and Patiria miniata. 



(b) Physically these eggs consist of a slightly viscous cyto- 

 plasm inclosed in a vitelline membrane of solid consistency. 



(c) In all three species the fertilization reaction begins at the 

 point of attachment of the successful sperm and is transmitted 

 from this place in all directions over the egg. 



(d} The visible manifestations of the fertilization reaction are 

 a roughening of the surface and the elevation of the vitelline 

 membrane. Both begin at the site of sperm entry and spread 

 from there over the egg. 



(e) The vitelline membrane is identical with and is elevated as 

 the fertilization membrane. 



(/) In fragments of eggs only that surface of the fragment which 

 was part of the original surface of the egg shows the fertiliza- 

 tion reaction-roughening and membrane elevation. 



(g) The vitelline membrane cannot be replaced or reformed. 



(//) At the moment of fertilization just preceding the elevation 

 of the vitelline membrane an increased viscosity or gelation occurs 

 in the egg. This splits the vitelline membrane from the egg 

 cytoplasm and provides a new resistant surface for the latter. 

 This gelation is the cause of the roughening of the egg at fertili- 

 zation. 



(i) A change in the egg thus precedes membrane elevation and 

 makes it probable that the latter process is not the primary event 

 in the fertilization reaction. 



(j) After membrane elevation by such artificial agents as 

 were tested there is no increased viscosity in the egg but the 

 cytoplasm is of the same or of less viscosity than the unfertilized 

 egg, until cytolysis occurs. 



