THE WORM-LIKE ANIMALS 



hitherto described. These animals live in calcareous (chalky) tubes, the apertures 

 of each tube being closed when the worm has retreated within by a tight-fitting 

 stopper, formed from a modified piece of one of the gills. The first tube made by 



COMMON SERPITLA, Serpulci contortuplicatd, 

 (Natural size.) 



the young worm is cylindrical and open at both ends, but as the animal increases 

 in size it enlarges and extends its tube by adding on layers of calcareous matter to 

 the aperture at the head end. The species of the allied genus Sabella exude a gluey 



SABEHA, Amphicora sabella (enlarged 30 times). 



substance, and construct a flexible, leathery tube. In some cases these tubes are 

 covered with sand, or pieces of shell, and completely resemble those of the Tere- 

 bellidce. The species of the genus Amphicora may be found among seaweed on the 



