In connection with the inquiries which I undertook at the beginning of the present year into the question of the destruction of immature fish I have been investigating since the issue of the last number of the Journal the development of eggs in the ovary of some flat fishes and the history of the ovary before and after maturity is attained. I have made it my special object to trace the history of the ovary from one spawning period to the next, in order that it might be possible to understand more clearly than at present, from the appearance of an ovary examined at any given time, in what stage of development it was. Mr. Holt has made some observations on this subject, and discussed them in his paper in the number of this Journal for November, 1892. He states there that the first approach to maturity in the ovary is denoted by an enlargement of some of the ova, and the assumption by them of an opaque condition. He terms those ova which have begun to get opaque, “active,” and those which have not, “inactive.” In a footnote it is stated that the changes which give rise to the opaque condition are not the same in all species, but that they appear to possess the same significance. Mr. Holt leaves undecided the question whether all the active ova are expelled during the spawning period, so that there is a period following the process of spawning when only “inactive” ova being present, the condition of the ovary is not distinguished by internal structure from that of a fish which has not begun to breed, which is immature.