INTRODUCTION. 75 



security, and seldom leave it even though disturbed. 

 Although weak and languid, they are continually 

 giving various movements to the body, but without 

 shifting their station. The back is sometimes bent 

 outwards, and soon after resumes its natural position, 

 and the head is elevated, and speedily drawn down 

 again. At other times, the anterior part of the body 

 makes two or three very rapid vibrations to the right 

 or left ; while less perceptible motions are communi- 

 cated to the different rings, some of which are consi- 

 derably dilated, and others contracted. The effect of 

 these alternate swellings and contractions soon be- 

 comes apparent, for the outer skin, now rendered dry 

 and rigid, by the subtraction of the juices by which it 

 was previously nourished, begins to split on the back 

 of the second or third segment, and discloses a por- 

 tion of the new integument. The rent being once 

 commenced, is easily extended by the dilatation of 

 the body, from the first to the fourth segment, and 

 thus leaves a considerable part of the back unco- 

 vered. This part of the body is no sooner free 

 than it is curved upwards, a movement by which the 

 head is disengaged from its old envelope, and raised 

 through the fissure. The head is then reclined on 

 the case that formerly contained it, and nothing re- 

 mains but to withdraw the hinder part of the body, 

 which is done by contracting the segments, and 

 drawing them towards the head till they reach the 

 opening. 



All these operations, apparently so laborious, are 



