A WIDESPREAD B CHROMOSOME POLYMORPHISM MAINTAINED WITHOUT APPARENT DRIVE.

The transmission rates of the three main types of B chromosome present in the grasshopper Eyprepocnemis plorans were studied by two different methods: (i) cytological observation of their meiotic behavior in males and females and (ii) karyological analysis of the embryo offspring obtained either from gravid females collected in the field or from controlled crosses. We conclude that Bs are inherited in a random manner with no tendency toward accumulation or loss from either sex. The possible factors that might be responsible for the maintenance of this widespread polymorphism are discussed.