He observed various stages of their sexual development, and found that some of the animals were neither male, nor female, nor hermaphrodites, but represented a whole spectrum of gynandromorphism.

[6] His studies of the gypsy moth, which culminated in his 1934 monograph Lymantria, became the basis for his theory of sex determination, which he worked on from 1911 until 1931.

[2] Goldschmidt left Munich in 1914 for the position as head of the genetics section of the newly founded Kaiser Wilhelm Institute for Biology in Berlin.

[7] During a field trip to Japan in 1914, he was unable to return to Germany due to the outbreak of the First World War, and was detained as an enemy alien in the United States.

Sensing that it was unsafe for him to remain in Germany, he emigrated in 1936 to the United States, where he became a professor at the University of California, Berkeley.

His ideas about macromutations became known as the "hopeful monster" hypothesis, a type of saltational evolution, and attracted widespread ridicule.

Goldschmidt presented his hypothesis when neo-Darwinism was becoming dominant in the 1940s and 1950s, and strongly protested against the strict gradualism of neo-Darwinian theorists.

[14] However, there has been a recent interest in the ideas of Goldschmidt in the field of evolutionary developmental biology, as some scientists, such as Günter Theißen and Scott F. Gilbert, are convinced he was not entirely wrong.