In the small "Fly Room" at Columbia University, T.H. Morgan and his students, A.H. Sturtevant, C.B. Bridges, and H.J. Muller, carried out the work that laid the foundations of modern, chromosomal genetics. The excitement of those times, when the whole field of genetics was being created, is captured in this book, written in 1965 by one of those present at the beginning. His account is one of the few authoritative, analytic works on the early history of genetics. This attractive reprint is accompanied by a website offering full-text versions of the key papers discussed in the book, including the world's first genetic map.