SERPUL.E SABELL^E. 



tube they inhabit; most of them neither 

 walk nor swim, and those that drag them- 

 selves along, do it by the assistance of 

 the long tentacles surrounding the mouth. 

 The tube varies in texture, in different 

 species. Sometimes it is formed by agglu- 

 tinating foreign substances, such as grains 

 of sand, small shells, or fragments of vari- 

 ous materials, by means of a secretion, 

 which exudes from the surface of the body, 

 and hardens into a tough membranous 

 substance, as is the case of Terebella 

 medusa, which constructs its tube by 

 cementing together minute shells, and other 

 small bodies. There is no muscular con- 

 nection between these animals and the 

 tubes they inhabit, so that the creature can 

 be readily withdrawn from its residence. 



17. In this order are placed the SER- 

 PUL.E, which live in calcareous tubes, vari- 

 ously contorted ; the anterior extremity of 

 the body is adorned by a crown of ap- 

 pendages like plumes : these animals are 

 found adhering to oysters and other mol- 



lusks. They are frequently found encrusting the surface of 

 stones, or other bodies, which have been immersed for any length 

 of time, at the bottom of the sea ; they are closed at one end, 

 and from the opposite extremity the head of the worm is occa- 

 sionally protruded in search of nourishment. The SABELL^J also 

 belong to this order. They inhabit a tube, which is. most com- 

 monly composed of granules of clay or mud, and is rarely cal- 

 careous (fig. 80). The Dentalium, Terebella, Amphitrite, and 

 Syphostoma, are other genera of the order of Tubicola. 



17. What are serpulae ? What are sabella* ? 



Fig. 80. SABELLA. 



