ABSTRACT
It was realized in the very early days o f Mendelism that there is some connection between sex determination and Mendelian heredity. Even before the rediscovery o f Mendel’s2 work, Bateson in 1894 pointed out that sex is an example o f discontinuous variation, and included it in the body o f facts which, presented as Materials for the Study of Varia tion, nearly brought him independently to the idea of discontinuous hereditary units. Correns3 was the first to give an actual demonstration that the connection was a real one. He showed that in Bryonia the male is heterozygous for sex factors, and produces two classes o f pollen, while the female corresponds to the homozygous recessive. This was soon followed by the discovery o f unequal sex chromosomes by McClung.
