SERPULA. 123 



The concamerated varieties which are found 

 among- the Serpulae do not deserve a separate di- 

 vision, because the conformation appears to ori- 

 ginate not in any specific difference, but in an in- 

 stinctive desire of the animal, for some important 

 purpose, to increase the length of the shell with- 

 out materially adding to the size of his apartment. 

 The chambers are not connected with each other 

 by any siphunculus or opening; the last can there- 

 fore only be inhabited. No sign of the inter- 

 nal dissepiments is visible externally, except in 

 one species, S, Polythalamia. 



In this genus as well as in the preceding one, 

 the animal has been supposed to live with little or 

 no adhesion to his shell ; but the degree and mode 

 of his attachment are doubtless as various as the 

 peculiar specific forms. 



