In some classical experiments on pea-breeding Mendel obtained the following frequencies for different kinds of seed in crosses with round yellow seeds and wrinkled green seeds: Observed Theoretical Round and yellow 315 312-75 Wrinkled and yellow 101 104-25 Round and green 108 104-25 Wrinkled and green 32 34-75 556 556-00 The column headed 'Theoretical' gives the numbers that would be expected on the Mendelian theory of inheritance, which predicts that the frequencies should be in proportions 9, 3, 3, 1. Can the difference between the observed and theoretical figures be ascribed to chance fluctuations? (Camb. N.S.)