ANNELIDA. 246 



l)y the contraction of the upper bands, which by 

 raising both ends of the body bend the back down- 

 wards. In proportion as the bands, situated on 

 either side, act in concert, while the others are 

 relaxed, the body will be bent laterally towards 

 that side. When all the four muscular bands con- 

 tract 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, also attached to the rings, 

 pass from the one to the other in 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 wholly elongated, according 

 as the actions of these oblique muscles are partially 

 or generally exerted. 



The skin on the surface of the earth-worm is 

 furnished, at the parts where it covers the rings, 

 with very minute bristles, called setce, by means 

 of which the animal is enabled to fix those parts 

 on the ground, while the other portions of its body 

 are in motion. These hairs, both in the anterior 

 and posterior segments, are directed towards the 

 centre of the animal ; while those on the middle 

 segments are perpendicular.* We almost con- 

 stantly find, in animals belonging to the order of 



* As an instance of the extraordinary multiplicity of species ex- 

 isting in every department of living nature, 1 may here notice, that 

 of the common earth-worm, apparently so uniform in its shape, 

 Savigny has lately, by a closer examination, been able to distinguish 

 no less than twenty-two different species, among those found in the 

 neighbourhood of Paris alone. 



