1Studies were made of the seasonal reproductive cycles of Chiton pe/liserpentis, Onithochiton quercinus and Plaxiphora paeteliana. All are dioecious and not sexually dimorphic. The sex ratio is 1 : 1 in P. paeteliana, but is biased 2 : 1 in favour of males in 0. quercinus and C. pelliserpentis.The two chitonid species exhibited a bimodal reproductive cycle: 0. quercinus spawned in spring and autumn, with a peak in autumn and C. pe/liserpentis spawned in spring and autumn, with a peak in spring. The mopaliid P. paeteliana spawned for several months in spring and autumn, and the nature of the pattern was less clear.Gametogenesis in all species occurred during periods of increasing sea temperatures in late spring and early summer and during periods of decreasing temperature in late autumn, in each case following spawning. Phytoplankton levels were high at the time of spawning, although the larvae are presumed to be lecithotrophic.

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