ANNELIDA. 273 



axis of the body. There are generally four 

 distinct bands provided ; two running along the 

 back, and two along the lower part of the 

 body. 



The effects which result from the action of 

 these muscles are such as might easily be anti- 

 cipated. The lower set must, when contracting, 

 bring the rings nearer to one another at that 

 lower part ; and when the whole series occupy- 

 ing that situation are exerted in concert, they 

 will raise the body in the form of an arch. An 

 opposite curvature will be produced by the con- 

 traction of the upper bands ; whereby the back 

 will be bent downwards, and both ends of the 

 body raised. In proportion as the two bands, 

 situated on each side, act in concert, while the 

 others are relaxed, the body will be bent late- 

 rally towards that side. When all the four 

 muscular bands contract together equally, their 

 joint effect will be to bring the rings near to 

 each other, and to contract the length of the 

 worm ; the skin being at the same time wrinkled 

 and swelled out between the rings. 



Other muscular bands, attached to the rings, 

 pass from the one to the other in more oblique 

 directions. By means of these muscles the 

 rings may be made to recede at some points, 

 while they approach at others ; so that the body 

 may be either twisted laterally on its axis, or 



VOL. I. T 



