In spite of the world-wide distribution and common occurrence of Aurelia aurita, the details of its reproductive ground have little been given. A series of work to make the reproductive ground of this medusa clear was carried out in Urazoko Bay, a small inlet, situated in the eastern part of Wakasa Bay on the Japan Sea coast, in the period from November 1970 through April 1973.
The occurrence patterns of early liberated ephyrae, metephyrae and young medusae at their maximum season were respectively checked by examining the samples collected by means of vertical hauls of a plankton-net (45cm in mouth diameter and 0.33mm in mesh szie) at each of the stations settled in the bay (Fig. 1). The settlements of planulae and early polyps were examined by monthly observations throughout the breeding season from late November 1970 through July 1971, using the collectors made of five upper shells of Pecten albicans and hung at the depth of 0, 2, 5 and 10 meters (Fig. 3) from the rafts which were set at each of the stations in the bay (Fig. 2). The results obtained are summarized as follows:
1) Early ephyrae were mainly distributed in the inner part of the inlet or the coastal shallow areas of the waters (Figs. 4 and 5).
2) Planulae and early polyps were found on the collectors in the inner part of the bay from January to June, most abundantly between the surface and 5 meter layer (Fig. 6).
3) According to these results and the distribution patterns of marine plants in the bay, it will be concluded that the reproductive ground of this medusa in the bay is the areas that are covered with marine plants such as Sargassum and Zostera (Figs. 8 and 9).
