406 HOMES WITHOUT HANDS. 



serpula is very close, the animal may easily be distinguished by 

 the absence of the beautiful operculum or stopper, which forms 

 so conspicuous a feature in the serpula. 



Peehaps the most plentiful species of this genus is the 

 common Sabella {Sabella alveolaria), which may be found in 

 countless myriads on many of our coasts. On several sandy 

 shores, especially those of the southern coast, the wanderer by 

 the sea may perceive masses of hard, agglutinated sand, pierced 

 with innumerable holes. These masses are of great size, and in 

 some places are strong enough to bear the pressure of a foot, 

 though in others a slight push with the hand is sufficient to 

 detach a portion. 



If this perforated sand be closely examined, it will be seen to 

 consist of a vast number of tubes, which are fixed together, 

 and are further consolidated by sand which has washed over 

 them, and lodged between them. When the water covers the 

 sand mass, a delicate feathery ttift is seen to protrude from each 

 hole, so that the general aspect is full of beauty. These tufts are 

 the tentacles of the Sabella, and when examined with a micro- 

 scope of moderate power, each tentacle is seen to be composed 

 of a central shaft, with projecting teeth or fringes on both sides. 

 There are about eighty of these tentacles, and as they are 

 extremely flexible and always in motion, their appearance is 

 peculiarly elegant. 



Nothing is easier than to examine the structure of this 

 Sabella, though the task of isolating a single tube is not an easy 

 one. A penknife wHl soon break up the tube, and a pair of 

 forceps will readily pull out the inhabitant, in spite of the array of 

 bristles and hooks wherewith it clings to its habitation. It is 

 but a little creature in point of length, but in point of width it 

 nearly fills the diameter of the tube. The extremity of the 

 body, however, is very small and slender, and is doubled back 

 upon itself, with its tip pointing to the mouth of the tube. 



The structure of the tube is extremely variable. Some indi- 

 viduals seem to give all their endeavours towards making their 

 dwelling as long and strong as possible, while others are content 

 with a tube which is barely long enough to shelter the whole 

 body. They work with great rapidity, and when confined in an 

 aquarium, will build their sandy homes uearly as well as if they 



