CHAPTER XVIII 



THE MARINE WORMS 



As contrasted with the comparatively few kinds of worms which 

 live in fresh water, we find that the sea is rich both in segmented 

 and unsegmented forms, which reach a considerable size, and 

 are often beautiful in colour. Perhaps the majority indeed are 

 beautifully coloured, as compared with the ugly earthworm, 

 and some are genuine ornaments of the aquarium. Only a few 

 can be mentioned here, and it should be noticed in the first place 

 that, as a general rule, the worms of the sea are prized as food by 

 fishes and other animals. The consequence is that very many 

 make for themselves special protective tubes, sometimes of 

 fragments of sand, sometimes of lime, while others bury themselves 

 in the sand or mud, or hide under rocks and stones. The result of 

 this again is that the marine worms require to be carefully looked 

 for, and may be readily overlooked. As a rule, the sand and 

 mud-haunting forms are not suitable for the aquarium, and one 

 is thus practically limited to the tube-inhabiting species and a few 

 of the free-living forms. Many of the latter will not thrive in 

 captivity, and those which can be induced to live there are so 

 persistently shy in their habits that not much can be made of 

 them. The tube-inhabiting forms, on the other hand, must 

 protrude part of the body from the tube into the water in search 

 of food, and in order to expose the gills to the purifying action of 

 the water, and where they can be made to flourish are instructive 

 and interesting. 



Of the free-living worms we shall mention only the leaf- 

 worms, which if not the commonest are at least very common, 

 and are easy to keep in confinement. There are a considerable 

 number of these leaf-worms, and all can be recognised by the 

 leaf-like plates at the sides of the body. The marine worms as a 



general rule have attached to each ring of the body a pair of out- 



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