Arp attains his "decisive forms" in April 1917: "In Ascona I made drawings of [..] branches, roots, grass, rocks [..]. I simplified them and combined their nature in emotional oval allegories of the body's transformation and becoming." Arp initially renders this intention to illustrate nature's constant process of transformation in reliefs and works on paper, before he discovered that the round plastic was his most suitable means in 1929. This medium allowed him to illustrates becoming and decay in form of softly flowing, merging masses. He, who has always been occupied with philosophy and psychology, attains a synthesis of Surrealism and abstraction.