28 EARTHWORMS AND THEIR ALLIES [ch. 



with the single or double spermatheca. This is 

 usually a large sac, always single or consisting of one 

 pair only, which opens on to the exterior close to the 

 oviducal pores ; these spermathecae in the Eudrilidae 

 are not comparable to the spermathecae of other 

 earthworms ; for they are in a way comparable to the 

 sperm sacs, being formed as outgrowths of the septa. 

 There is some variation of structure within the family. 

 In a number which are associated into a sub-family 

 Eudrilacea there are two paired calciferous glands 

 and a single unpaired one, while the paired nephridia 

 open by a large pore on to the exterior. In a 

 parallel sub-family, the Pareudrilacea, the calciferous 

 glands are apt to be more numerous and have a 

 totally different structure : they have been apparently 

 converted into non-digestive glands bearing some 

 relation to the vascular system. The nephridia 

 moreover do not open on to the exterior by single 

 pores, but form a network within the thickness of the 

 body wall and then open by numerous pores. There 

 is however no resemblance here to the micronephridia 

 of Dichogaster and other Megascolecids. In Libyo- 

 drilus (as an example of the Pareudrilacea) each 

 nephridium forms a network out of the duct leading 

 to the exterior. In the interior of the body a series 

 of paired meganephridia are visible. 



The earthworms of Europe belonging to the family 

 Lumbricidae offer again a rather different type of 



