THE WARM‐WATER LUGWORMS OF THE WORLD (ARENICOLIDAE, POLYCHAETA)

It was recently shown, by observations made in the Woods Hole region, that the currently accepted definition of Arenicola cristata embraces in fact two species, A. cristata Stimpson and A. caroledna Wells. The distribution of these forms has now been studied. A. cristata is the dominant warm‐water lugworm on the shores of North America, extending northwards to Woods Hole, Massachusetts, and Humboldt Bay, California. A. caroledna dominates in China and Japan. But both species are very widely distributed round the world, and both show a tendency to differentiate into local varieties. Arenicola glasselli Berkeley and A. bombayensis Kewalramani et al . are intimately related to caroledm , but should be maintained, for the present at least, as separate species. The four species cristata, caroledna, glasselli and bombayensis form a compact, closelyrelated quartet, which monopolises the lugworm beaches of tropical and subtropical shores. In Bermuda, A. cristata was collected from purely calcareous “sand”, though elsewhere it occurs in more usual littoral sediments. Arenicola loveni Kinberg is a warm‐temperate form, not very closely related to the four named above, and found to the south of the zone which they occupy. The Australian specimens constitute a seperate subspecies from the African ones, even though the “septal gonad” on which the distinction was origmally based by Stach is probably a temporary local accumulation of germ cells associated with the act of spawning. During the work, two remarkable anomalous worms were noticed: a Neapolitan A. cristuta from which either the 5th or the 6th setiger seems to have disappeared without trace, and an A. bombayenais with two pairs of hearts.