title: Penetration of zone-free eggs by spermatozoa of different species.
mesh_terms: D000818:Animals; D006224:Cricetinae; D005260:Female; D005306:Fertilization; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008858:Microscopy, Phase-Contrast; D010063:Ovum; D051381:Rats; D013045:Species Specificity; D013075:Sperm Capacitation; D013094:Spermatozoa