Some Curious Tube-builders. 



towards the trowels, while another organ, perhaps the 

 mouth, is also occupied, it may be, in compounding 

 the preparation with adhesive matter. Still does the 

 partial or complete revolution of the plume above, and 

 of the body within the tube, continue ; the bulk of 

 the muddy mass diminishes, activity abates ; it is suc- 

 ceeded by repose, when the tube is found to have 

 received evident prolongation." 



Though not such a handsome worm as the Fan 

 Sabella, the little " Sand-mason " worm builds a far 

 more elaborate tube, using grains of sand, small pebbles, 

 and fragments of shell in its construction. The Sand- 

 mason worm has upon its head a large number of 

 long thread-like feelers arranged about its mouth, each 

 feeler having a groove running down its whole length, 

 while the gills are short, branched, and restricted 

 to two or three pairs in number. The very slender 

 feelers, or tentacles, can be extended for a surprisingly 

 long distance, and are used by the Sand-mason in 

 collecting the materials for constructing its tube. When 

 one of these tentacles in sweeping about grasps a frag- 

 ment of shell or a grain of sand, the object may be seen 

 to travel along the groove, running down the entire 

 length of the tentacle, until it reaches the mouth of the 

 worm. The little Sand-mason takes in turn each 

 fragment so obtained into its mouth, and then the 

 grain of sand or fragment of shell, as the case may be, 

 is apparently moistened with some sort of adhesive 

 secretion, and is then ejected and placed in position 

 on the edge of the tube, being arranged in its place 

 by the lips of the worm. With tireless energy, grain 

 by grain is collected by the little Sand-mason and 



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