4 EARTHWORMS AND THEIR ALLIES [ch. 



This earthworm is a native of Guatemala and is 

 some six inches in length with a diameter of perhaps 

 a quarter of an inch. The front part of the body is 

 thicker than posteriorly. The body will be seen to 

 be divided into some 218 rings by circular furrows 

 which run right round the body. These divisions are 



Fig. 2. Fig. 3. 



Fig. 2. The same species ; first two segments and prostomium shown 

 from ventral surface, I prostomium, II first segment without any 

 setae, III second segment with its four pairs of setae (the dorsal- 

 most seta of each outer pair is not visible in this view). 



Fig. 3. A section through the body of the same species showing the 

 ventral position of the pairs of setae. (After Eisen.) 



termed segments or somites. At the head the mouth 

 is surrounded by the first of these, and on the dorsal 

 surface of that segment is a projection like an in- 

 complete segment which is known as the prostomium. 

 From the xmth segment to the middle of the xxth 

 the body has a different appearance, and this region is 



