Factors Affecting Vertebral Variation in Mice

T H E historic controversy between 'spermists' and 'ovists' ended towards the close of the eighteenth century in a partial victory for both sides: sperm and egg were shown to be alike necessary for the genesis of a new individual. But the question of the relative biological contribution of the male and female parent remained open. A century later the biometrical school of Karl Pearson showed that in human stature, and a number of related characters, the respective influences of the mother and the father upon the offspring were of equal strength. The rediscovery at this time of Mendel's work seemed to offer the final and decisive proof of sex equality in heredity, for according to Mendel's system the number of hereditary factors supplied by each parent was of necessity equal.