100 OLIGOCHAETA 



concern (i) theii- position in the body, (a) the point of opening on to the exterior, (3) the 

 degree to -which the ducts of one side of the body are fused together. 



As a general rule the sperm-ducts lie in the body cavity ; this is always 

 the case in the lower Oligochaeta where they are frequently much coiled ; even 

 in the higher Oligochaeta (earthworms) where the ducts (except in Moniligaater) pass 

 in an approximately straight course from funnel to pore, the sperm-ducts lie a little 

 above the ventral parietes^ 



In Lumbricus (cf. Neuland, fig. 4) and other forms the sperm-ducts lie just 

 within the peritoneum. 



The sperm-ducts lie deeper still within the tissues of the body-wall in a few 

 other earthworms. I found this to be the case with Acanthodrilus annectens and 

 have since recognized the same thing in Acanthodrilus paludosus and in a worm 

 belonging to a totally different family, viz. Siphonogaster millsoni; in these examples 

 as well as in Diplocardia communis (Gabman, 1) the sperm-ducts are imbedded deep 

 within the longitudinal muscular layer. It is quite possible that in other earthworms 

 whose sperm-ducts have not been seen, the reason for their invisibility in a dissection 

 is due to their lying in this position. 



Finally the genus Sparganophilus (Fam. Geoscolicidae) is unique by reason of 

 the fact that the sperm-ducts lie deeper still or more superficially in reality. ■ They 

 are placed just beneath the epidermis; in the clitellar region the duct hes at first 

 below the entire epithelium ; nearer to the pore it comes to be just underneath the 

 superficial epidermis of the clitellum. 



The position of the external orifice differs greatly and is but rarely characteristic 

 of a family. As a general rule the two sperm-di«3ts of each side unite to form a single 

 tube with a single orifice. In Phreoryctes, however, the two sperm-ducts open on 

 to as many consecutive segments ; they have absolutely no connexion with each 

 other. An intermediate condition is to be seen in the genus Pelodrilus ; here there 

 are two quite separate sperm-ducts which, however, open near to each other on the 

 same segment. In the Acanthodrilidae there is a still more marked foreshadowing 

 of a fusion between the two sperm-ducts, for they join just before the external 

 orifice. In the majority of earthworms, for example in the Perichaetidae, the two 

 sperm-ducts join as soon as they can, i. e. in the twelfth segment. 



§ 5. Oviducts. 



In the lower Oligochaeta there are no special conduits for the ova ; the genus 

 Aeolosoma is provided with a pore upon the median ventral surface of the sixth 



