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Show 1904.] MARINE FAUNA OF ZAXZIBAR. 313 berg's collection from the Red Sea but one fragment occurred, in Gravier's three specimens, all small, while only one specimen is contained in the collections made by Semper in the Philippines. The worm presents distinct variations in correspondence with its habitat. The five largest specimens, measuring 100 m m . by 5 or 6 inclusive of the feet, were obtained by digging in the beach of clean and rather coarse sand, just below7 the British Agency at Zanzibar, which appeared to be habitable to them and to Diopcttrct neapolitana alone. These were of a, pink or flesh-colour with sparsely scattered specks of brown pigment. Many specimens of all sizes up to that given above were found on the shore, and dredged from among sponge and Alcyonaria &c, at a depth of 10 fathoms in Wasin Harbour. Of these some were similarly coloured, but in many others the brown pigment was more or less uniformly developed, so that the body was of a metallic brown with wdiite spots, of which one in the middle of each segment dorsally was especially prominent. The gills were white even in life, but this loss of colour may have been accidental owing to the de-oxidation of the water in which they were kept before examination. At low spring-tide level in Chuaka Bay the worm is very common, living in the dense tufts of Halimeda which are so abundant there, and in the cavities of sponges. All have Text-fig. 56. E. antennata, in the act of swimming. developed more or less green tint, in some only about the head, but in the majority the whole body is of a fine dark green colour harmonising well with that of the Halimeda. None of the specimens found here attain to the size of those from the sand at Zanzibar, the largest of these measuring 80 m m . x 4. When disturbed the worms swim by coiling the body in the way shown in text-fig. 56, the coil passing down to the tail and being then formed afresh at the head, a peculiar mode of motion also |