title: Ultrastructure of species-foreign spermatozoa after penetrating the sea urchin oocyte.
mesh_terms: D000818:Animals; D049872:Bivalvia; D005306:Fertilization; D008297:Male; D010986:Platyhelminths; D012617:Sea Urchins; D013045:Species Specificity; D013094:Spermatozoa / Q000166:cytology*