Prof. M. Hudinaga initiated studies on the hatching and early stage raising of the prawn. It was possible for him to produce 15,000,000 juveniles or 20-day-old post-larvae in 1963. Regarding the detailed procedure of the technique and its application in field practices, there are several reports by Hudinaga and Prof. K. Miyamura, Hudinaga and Kittaka, and Kunihiko Shigeno. The account given in this treatise is based mainly on the works of these authors, particularly those pertaining to the seedling production in Himejima of Oita Prefecture. If it is intended to grow prawns from the seedlings obtained early in the year so that they attain marketable size at the end of the year it is necessary to obtain gravid prawns and to induce early hatching. Gravid prawns appear in the early spring in Kagoshima, Miyazaki and Kochi where the water temperature rises on account of the Black Current.