240 STRANGE DWELLINGS. 



formed, in which the object is securely held by atmospheric 

 pressure ; this power is, however, immediately aided by the con- 

 traction of the circular muscular fibres. Such, then, are the 

 marvellous instruments by which these peaceful worms construct 

 their habitations, and probably sweep their vicinity for food.' 



It is a remarkable fact that the Terebella does not form tubes 

 during the early portions of its life, but swims about freely, like 

 the nereis and other marine annelids. It has a head, eyes, feet, 

 and antennae, and roams about at will ; whereas, in its perfect 

 state, it has neither head, nor eyes, nor antennae, nor true feet, 

 the last-mentioned organs being modified into the tufts of hooks, 

 and bristles, by means of which it moves up and down its tube. 

 The reader may perhaps remember that the barnacles and many 

 other stationary marine animals are free during their prelimi- 

 nary epochs, and only become fixed when they attain the perfect 

 form. To our minds, the former seems the more perfect, and 

 certainly the more agreeable state of existence ; but we cannot 

 measure the feelings of such an animal by our own, and may be 

 sure tliat the creature enjoys existence as much while shut up 

 in a tube, as when roaming the ocean at liberty. 



Another species, Terebella figuhis^ sometimes called the 

 Potter, prefers mud as the material for its dwelling, and con- 

 trives to make the dark sea-mud so adhesive that it is capable 

 of being formed into a tube. 



As may be easily imagined, this tube is extremely fragile, and 

 cannot be removed entire from the water without the exercise 

 of much care, it.«i own weight being mostly sufficient to tear it 

 asunder. The walls of the tube are tolerably thick, and the tube 

 itself is of some size, measuring nearly half an inch across, and 

 is always found to be protected by the earth upon which it is 

 placed. It is a rather curious fact that the tentacles of this 

 species are of extraordmary length, extending for some eight or 

 nine inches beyond the entrance of the tube, the animal itself 

 measuring little more than four inches in length. 



The last species of Terebella tliat will be mentioned, is a very 



