THE BIOLOGY OF THE CELL SURFACE 



cones may be exaggerated in unripe echinoderm eggs, i.e., 

 those incapable of fertilization and development (Fig. 31). 



Fig. 31. — Ectoplasniic changes in unripe eggs in response to sperm-entry, a, egg 

 of a starfish (after Schneider); b, egg of a holothurian (after Iwanzoff). 



The cones may be made more expressed under experimental 

 conditions.^ In the second place, the sperm-nucleus having 

 reached the egg-nucleus forms with it the zygote- or 



^ Fol, iS/Q; Schneider, i8g^; Iwanzoff, i8g8; Just, Tg2Qb. \.^^^^ 



