342 TOILERS IN THE SEA. 



nut-shell. These valves are immoveable, and pro- 

 tect the weak part of the animal. All the internal 

 organs of the Teredo are placed one immediately 

 behind the other, a position which is necessitated 

 by the narrowness of the body, and the repeated 

 elongations which it is required to undergo." 



" The Teredo deposits greenish-yellow eggs, which 

 are spherical. As soon as the larva is born, it 

 becomes covered with vibratory cilia. It swims 

 with facility, rises and falls in the water, seeking for 

 wood into which it may penetrate. When it has 

 found a piece of wood to suit its convenience, it walks 

 tip and down on its surface, like a caterpillar. From 

 time to time it opens its little valves, as if practising 

 for the mining operations its contemplates. At last 

 it fixes upon a place, and makes an incision. In 

 due time it has excavated a hole, capable of con- 

 taining half its body. The young Teredo now 

 covers itself with a coating of mucous matter, which, 

 condensing by degrees, at last forms a resisting shell. 

 In this covering two or three holes are left, for the 

 projection of the syphons. About the third day the 

 tube has become solid, and it is now the origin of 

 the tube of the animal. We cannot see what is 

 taking place inside, for this coat is opaque ; but if 

 we detach some of the young Teredos from the wood 

 at this stage of their development, we shall find that 

 -there has been secreted a new shell, similar in all 



