THE SHELL-BINDER TEEEBELLA. 425 



whicli it is built. Generally the fragments of shell are very- 

 small, no larger, indeed, than those of which the well-known shell- 

 sand is composed. But, in many instances, the Terebella has 

 been known to choose shells in an entire state, and thus to give 

 its tube a very extraordinary aspect. 



The process of tube-making is conducted with much rapidity. 

 Supposing that, as is often the case, a storm has arisen, and wash- 

 ed away the projecting portion of the tube, the Terebella sets to 

 work to make a new portion in lieu of that which has been de- 

 stroyed. Spreading out its long and delicate tentacles in all di- 

 rections, it brings the materials toward its mouth, and always ap- 

 portions the number of tentacles employed to the load which is to 

 be carried. Having brought the materials within reach, it ar- 

 ranges them in regular circles, agglutinating them together with 

 some secretion which has the property of hardening under water 

 into a gelatinous substance. The union of these two materials — 

 namely, the gelatinous secretion and the shells which are fastened 

 to it — gives to the tube the two needful qualities of strength and 

 flexibility. 



Small particles of shell are generally affixed by the whole of 

 their surface, but the large pieces are only fastened by one edge, 

 so that a tube that is made wholly of large fragments looks as if 

 it were covered with scales, like those of a serpent. 



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 preliminary 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 can not measure the 

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

 creature enjoys existence as much while shut up in a tube as 

 when roaming the ocean at liberty. 



Another species, Terebella figulus, sometimes called the Pot- 

 ter, prefers mud as the material for its dwelling, and contrives to 



