Abstract
Three diffusible substances were found by Ephrussi and Beadle to be involved in the development of wild type eye color in D. melanogaster. A summary is given of the present state of the knowledge of these substances (Dec, 1936), including: (1) their nature, (2) time of appearance in the body fluid of the fly, (3) sources in the fly, and (4) possible relations of various genes to these three substances.