330 TOILERS IN THE SEA. 



that the eggs, involved in a mass of jelly, are 

 extruded, in their season, from the upper aperture of 

 the tube. Nourished in this jelly, they rapidly pass 

 through the foetal metamorphoses, and attain the 

 annelidan form so soon as they are free, or, at least, 

 before they are more than two lines in length. The 

 first instinct constrains and enables the infant worm 

 to build, out of the mud around it, a tiny case to 

 shield the body ; and this is in future always carried 

 onwards as an advanced work, so as rather to 

 receive the body, as it grows, than to wait upon that 

 growth. The growth is rapid ; and the external 

 organs, as well as the rings of the serpentine abdo- 

 men, are involved in succession. Thus the worm 

 has at first few segments, and the ornaments of the 

 head may have no more than six filaments. These 

 two are, on their first appearance, simple ; and it is 

 a subsequent development that fringes them with 

 cilia, and makes the organ pectinated. When mature 

 a well-fed specimen may have ninety-two filaments 

 in each of the fans of the branchial tuft that adorns 

 the head ; and the body may consist of not fewer 

 than three hundred and fifty rings, each with their 

 pair of pencilled feet, and ringlets of many hooklets. 

 Such a specimen will be fifteen inches in length, and 

 the tube will be two feet." 



" The tube is essential to the existence of its 

 tenant. The part first formed, to fit it for its 



