part of Tokyo Bay, Japan

The survivorship and daily production rate of the Aurelia aurita ephyrae population in Tokyo Bay was estimated. A disc growth index, expressed as the ratio of the diameter of the central disc to the diameter over lappet tips, was used to describe the developmental process and morpho logical changes in the ephyrae. The number of days spent of the arbitrary developmental stages as defined by disc growth index group was also calculated, and it appears that newly liberated ephyrae