The polyspermy block in eggs of Urechis caupo. Evidence for a "rapid" block.
D000818:Animals; D002455:Cell Division; D002467:Cell Nucleus; D005260:Female; D005306:Fertilization; D006376:Helminths / Q000502:physiology*; D007700:Kinetics; D008297:Male; D010063:Ovum / Q000502:physiology*; D012623:Seawater; D013094:Spermatozoa / Q000502:physiology*