appeared to support de Vries. The offspring had a smooth random distribution. Johanssen believed that his results showed that continuous variability was not inherited, so evolution must rely on discontinuous mutations, as de Vries had argued. Johanssen published his work in Danish in a 1903 paper Om arvelighed i samfund og i rene linier (On inheritance in populations and in pure lines), and in his 1905 book Arvelighedslærens Elementer (The Elements of Heredity). Punnett's mimicry, 1915 In 1915, Reginald Punnett argued in his book Mimicry in Butterflies that the 3 morphs (forms) of the butterfly Papilio polytes, which mimic different host species of butterfly, demonstrated discontinuous evolution in action. The different forms existed in a stable polymorphism controlled by 2 Mendelian factors (genes). The alleles of these genes were certainly discontinuous, so Punnett supposed that they must have evolved in discontinuous leaps. The undermining of mutationism Yule's analysis of Mendelism and continuous variation, 1902 The undermining of mutationism began almost at once, in 1902, as the statistician Udny Yule analysed Mendel's theory and showed that given full dominance of one allele over another, a 3:1 ratio of alleles would be sustained indefinitely. This meant that the recessive allele could remain in the population with no need to invoke mutation. He also showed that given multiple factors, Mendel's theory enabled continuous variation, as indeed Mendel had suggested, removing the central plank of the mutationist theory, and criticised Bateson's confrontational approach. However, the "excellent" paper did not prevent the Mendelians and the biometricians from falling out. Nilsson-Ehle's experiments on Mendelian inheritance and continuous variation, 1908 The Swedish geneticist H. Nilsson-Ehle demonstrated in 1908, in a paper published in German in a Swedish journal, Einige Ergebnisse von Kreuzungen bei Hafer und Weizen (Observations on Crosses in Oats and Wheat), that continuous variation could readily be produced by multiple Mendelian genes. He found numerous Mendelian 3:1 ratios, implying a dominant and a recessive allele, in oats and wheat; a 15:1 ratio for a cross of oat varieties with black and white glumes respectively, implying two pairs of alleles (two Mendelian factors); and that crossing a red-grained Swedish velvet wheat with a white one gave in the third (F3) generation the complex signature of ratios expected of three factors at once, with 37 grains giving only red offspring, 8 giving 63:1 in their offspring, 12 giving 15:1, and 6 giving 3:1. There weren't any grains