Roux investigated why the nucleus undergoes the precise division of mitosis while the rest of the cell undergoes a rather crude division when one cell splits into two. He argued that mitosis ensures a precise halving of the nucleus, suggesting that the nucleus contains the material basis of heredity.

Roux is regarded as the founder of developmental mechanics (“Entwicklungsmechanik” as he named it). His work on the production of half-embryos initiated a turning point by shifting emphasis from descriptive to experimental embryology. Roux believed that the above work showed that the nucleus of each blastomere is capable of directing a specific independent line of differentiation. He eventually concluded that the nucleus is made up of hereditary particles. Partial English translation in No. 534.3.