A Linear Time Algorithm for Triangulating a Point-Visible Polygon

Abstract

In the pulmonate snail Lymnaea stagnalis the neurosecretory caudo-dorsal cells (CDC) produce an ovulation hormone (CDCH) which is released at the periphery of the cerebral commissure (COM). Time schedules of the successive stages of the egg mass production following CDCH injection (COM extract) were determined at 20 degrees. Ovulation is performed rapidly, within 10 to 20 min. The latencies of the other stages are: egg formation, 20-30 min; egg mass formation, 60-90 min; and oviposition, about 120 min. The duration of oviposition is dependent on the size of the egg mass and varies from 5 to 20 min. At a 16-hr photoperiod all stages start 10 min earlier than at a 12-hr photoperiod. It is suggested that the effect of the photoperiod is achieved by a change of release activities of dorsal bodies and/or of CDC. The possibility that a nervous mechanism is involved in the control of the packaging of the egg cells is discussed.