During the past twenty-five years and more the house-fly, Musca domestica, L., has received much attention from entomologists, medical men, sanitarians and other investigators, and many observations on the life-history, habits, etc., of this fly have been made by individuals in different parts of the world. As a result of the investigations carried out during this period much information has been accumulated regarding the biology of this dangerous nuisance to mankind. However, notwith-standing all these observations and the great amount of knowledge that has been gained, there are a few points that have remained more or less indefinite. One of these is concerning the oviposition of the female fly; the number of eggs deposited during her life-period and the time elapsing between depositions.