1904.] 



MARINE FAUNA OF ZANZIBAR. 



3i; 



bei'g's collection from the Red iSea but one fragment occiuTed, in 

 Gravier's tlu'ee specimens, all small, while only one specimen is 

 contained in the collections made by Semper in the Philippines. 



The worm pi-esents distinct variations in correspondence witli 

 its habitat. The five largest specimens, measmnng 100 mm. by 

 5 or 6 inclusive of the feet, were obtained by digging in the beach 

 of clean and rather coarse sand, just below the British Agency at 

 Zanzibar, which appeared to be habitable to them and to Dwpatra 

 neapolitana alone. These were of a pink or flesh-colour with 

 spai'sely 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 similai4y 

 coloui'ed, but in many others the brown pigment was more or less 

 uniformly developed, so that the body was of a metallic brown with 

 white 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 Ohuaka 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. 



IS. antcmiata, in the act of swimmina'. 



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 

 hai'monising 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 mm. 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 

 foi'med afresh at the head, a peculiar mode of motion also 



