Abstract
The present paper deals with crossing experiments on translocation heterozygotes in the mosquitoCulex pipiens L. It is shown that the ratio of euploid and aneuploid gametes is determined by two allelomorphs of one single inheritable factor. These experiments agree with our hypothesis that the ratio of segregation types in a translocation heterozygous organism (alternate and adjacent) is determined by a series of multiple alleles of a single mendelian factor.