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POLYCHAETA 



their tenements, and these observations, though made nearly half 

 a century ago, have required very little addition or correction in 

 modern times. In speaking of Sdbella, he writes as follows : 



FIG. 152. 



FIG. 153. 



FIG. 152. The tube of 1'ectitiaria, auricoma. x 3. 

 (From M'Intosh.) This is its natural position as 

 carried about by the animal. 



FIG. 1 53. The upper end of the tube of Terebelln coii- 

 chileya. Slightly enlarged. (From M'Intosh.) 



" Let a tall and ample crystal jar containing a Sdbella be 

 emptied of its contents and speedily replenished with sea-water ; 

 the animal, if in view, has retreated during the short interval , 

 the orifice of the tube is closed, all is at rest. But soon after 



