106 HOMES WITHOUT HANDS. 



from any loose materials that are within reach, and has by this 

 means earned its specific name of modioUna. 



In two remarkable genera the shell is very small and is 

 cemented to the base of a long shelly tube, through which the 

 siphon runs. The Clavagella is remarkable for the successive 

 frills that decorate the tube ; from three to six of these curious 

 appendages being seen in various specimens. These Mils are 

 formed by the orifice of the siphon when the tube is elongated. It 

 is a remarkable fact, that the left valve of the shell is always 

 cemented to the side of the burrow, so that the animal possesses 

 no locomotive power, and in all cases the shell is very small, and 

 sometimes scarcely visible. 



The Wateeing-pot Shell {Aspergillum), is well known to 

 conchologists. In this creature the shell is exceedingly small, 

 and so deeply sunk into the tube that only the umbo of each 

 valve is visible. The base of the tube is expanded into a 

 rounded and perforated disc, which bears a remarkable resem- 

 blance to the "rose" of a watering-pot, and its opposite ex- 

 tremity is mostly decorated with frills, from one to eight in 

 number. 



The reader will remember that the wood-boring pholas always 

 makes its burrow across the grain of the timber which it is com- 

 missioned to destroy. The Shipwoem {Teredo navalis), on the 

 contrary, always burrows mth the grain, and never makes a 

 transverse tunnel, unless turned from its course by some ob- 

 stacle, such as a nail, or the burrow of another Teredo. 



At first sight, few would perceive that the Shipworm belongs 

 to the same class as the oyster and the snail, for it is long, 

 slender, and worm-like in shape, from six to eight lines in 

 diameter, and nearly a foot in length. One end is rather larger 

 than the shaft, if we may use the term, and is furnished with a 

 pair of cm-ved and very narrow shell- valves, while the other is 

 divided into a forked apparatus containing the siphon. The 

 colour is greyish- white. 



Such is the aspect of the Shipworm when adult, but in its 

 early stages of existence it possesses a totally different form. 

 When it first issues from the sheltering mantle of its parent, it 

 is a little, round, lively object, covered with cilia, like a very 

 minute hedgehog, and, bj'^" the continual movement of these 



