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The Brown Alga Sargassum muticum, a native of Japan but also introduced into the Pacific waters of North America, was first found on the Isle of Wight off southern England in 1973, and has subsequently spread as far west as Plymouth. A large attached population is also present on the Channel coast of France. Marine biologists in England, fearful of its possible effect on indigenous marine organisms and recreational amenities, set up an eradication programme. This was largely unsuccessful, even though an estimated 450 tonnes of wet S. muticum were collected in one year (1976).Some of the possible vectors of dispersal of this Alga are discussed, especially in relation to movement of oysters and shipping. It is thought that the spread of S. muticum will continue along the coast and that it may well extend deeper into the sublittoral than appears to be the case at present.A research programme on the ecology and biology of S. muticum, as well as on possible means of control, is continuing.

The Japanese Sargassum recently established at Portsmouth, U.K., is described and figured. It commonly bears two spirorbids which are new to Europe. One, Janua (Dexiospira) brasiliensis (Grube) =Dexiospira oshoroensis Uchida, is widespread in warm latitudes, whilst the other, Pileolaria rosepigmentata (Uchida), was previously known only from Japan. The former is distinguished from J. (D.) pseudocorrugata (=Spirorbis corrugalus) principally by its more opaque brood chamber and shorter, wider juvenile talon. The latter is one of the Pileolaria moerchi complex and can be recognised by its bilobed brood chamber, conical juvenile talon and single diffuse patch of pigment.