10 EARTHWORMS AND THEIR ALLIES fcH. i 



contractile. There are other branches of these main 

 longitudinal trunks and some minor longitudinal 

 trunks which we shall not stop to describe further. 

 The nervous system of the worm consists of a pair of 

 ganglia which lie above the gut in the third segment ; 

 they are connected by a commissure running round 

 the gut with a chain of closely fused pairs of ganglia, 

 one for each segment to the very end of the body. 

 In each of the segments, except the first two or three, 

 there are a pair of excretory organs known as 

 nephridia ; these are essentially coiled glandular 

 tubes opening on to the exterior by the regularly 

 placed pores already referred to in considering the 

 external characters. The tube ends in a funnel- 

 shaped, and therefore dilated, mouth, which opens 

 into the segment in front of that which contains the 

 rest of the organ ; a nephridium therefore lies in two 

 segments. The only other important organs which 

 are left for consideration are those devoted to the 

 reproduction of the species. The essential organs are 

 the spermaries and the ovaries. Of the former there 

 are two pairs of minute whitish bodies which lie in 

 segments x and xi on either side of the nerve cord 

 attached to the anterior septal wall of their segments. 

 The ovaries are not in the following, but in the xiiith, 

 segment, and occupy an identical position in that 

 segment. A short tube with a funnel or trumpet- 

 shaped and wide orifice opens into the cavity of the 



