43 8 
WORMS. 
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 apertuie at the head-end. 
common serpula, Serpula contortuplicata (uat. size). 
The species of the allied genus Sabella exude a gluey 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 Terebellidce. The species of 
the genus Amphicora may be found amongst seaweed on the coasts of Europe. 
The body is short, measuring less than half an inch in length, and composed 
of a small number of bristle-tufted segments. Unlike the Serpulidce, the animal 
habitually leaves its membranous tube in search of food, when it appears as 
a lively little creature, moving with indifference and facility either forwards 
or backwards. 
