158 



FIRST BOOK OF ZOOLOGY. 



thread-like feelers on the head. If these worms are taken 

 from their tubes and placed in a plate of sea-water in which 



FIG. 146. ANTERIOR PORTION OF A SEA- WORM, WITH THE (ESOPHAGUS PROTRUDED. CB, 



(Esophagus ; .;', Jaws ; A, Head, 



are contained also particles of dirt or sand, they will begin 

 to build a new tube, and for this purpose the threads on the 

 head will stretch out like delicate rubber cords, and, becoming 

 entangled in the particles of dirt, will draw them toward the 

 head, when the appendages on the body will mould it around 

 them in the shape of a tube. 



B \ 



c 



I A 



FIG. 147. SEA-WORMS WHICH MAKE LIMY TUBES. A, Worm with Irregular Tube, the line 

 I indicates natural length ; -B, Worm with Spiral Tube, enlarged ; C, Piece of Sea- Weed, 

 showing the Appearance and Natural Size of these Spiral Tubes attached to it. 



Other worms deposit a hard, shelly tube of lime. Some 

 of these are irregular in shape, as in Fig. 147, A. Other 



