Some Curious Tube-builders. 



panded and gently swaying in the clear water, presents 

 a most charming appearance. A shadow passing over, 

 or a ripple on the surface of the pool, and in a flash 

 every head has disappeared within its tube and no sign 

 of life or animation remains. To enable it to make so 

 startlingly abrupt a descent into the safe recesses of 

 its tubular home, the Serpula is provided with a very 

 remarkable piece of apparatus consisting of four rows 

 of tiny hook-like appendages on various rings of the 

 body, shaped something like hedgers' little bill-hooks 

 with their edges cut into long teeth. These little 

 hooks are exceedingly minute, a magnifying power 

 of three hundred diameters being necessary to show 

 all the structure clearly under the microscope. The 

 late Mr. P. H. Gosse calculated that the Serpula has 

 about nineteen hundred of these hooks, each hook being 

 cut into seven teeth, so that something like thirteen 

 thousand to fourteen thousand tiny teeth catch on to 

 the lining of the tube to drag the worm down when 

 it suddenly disappears from view ; altogether, a most 

 wonderful contrivance for safe and rapid retreat. 



The Fan Sabella is an interesting little mason worm 

 of the seashore, delighting in situations where there 

 is a mixture of sand and mud ; and on such a stretch 

 of shore at extreme low tide one may often find a forest 

 of little tubes sticking up two or three inches above 

 the surface, composed of grains of sand and mud 

 cemented together. Beneath the surface these tubes 

 extend to a depth of eight or ten inches, the total 

 length of the tube averaging about twelve inches. 



Of the manner in which the Fan Sabella constructs 

 its tube, that fine old naturalist Sir John Dalyell has 



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