Summarizes the major early findings of Morgan’s Drosophila research group, which based its research on the rapidly reproducing small vinegar fly, Drosophila melanogaster, often called the fruit fly. This epoch-making book presented evidence that genes were arranged linearly on chromosomes, and that the Mendelian laws could be shown to be based on observable events occurring in cells. The group also showed that heredity could be studied rigorously and quantitatively. Morgan was awarded the Nobel Prize for Physiology or Medicine in 1933.

Order of authorship in the original publication: Morgan, Sturtevant, Muller, Bridges.
Digital facsimile from Biodiversity Heritage Library at this link.

Muller showed that radiation causes mutations that are passed on from one generation to the next. This was the first suggestion that inherited traits might be altered or controlled, and it created a sensation: “Man’s most precious substance, the hereditary material which he could pass on to his offspring, was now potentially in his control. X rays could speed up evolution,’ if not in practice at least in the headlines. Like the discoveries of Einstein and Rutherford, Muller’s tampering with a fundamental aspect of nature provoked the public awe.“(Carlson). See also Muller's follow-up paper, "The production of mutations in x-rays," Proc. Nat. Acad. Sci. 14 (1928) 714-26. 

In 1946 Muller was awarded the Nobel Prize in Physiology or Medicine "for the discovery of the production of mutations by means of X-ray irradiation."

Muller was one of the earliest proponents of a genetics-first theory for the origin of life.