100 OLIGOCHAETA 



concern (i) their position in the body, (2) 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 Moniligaster) 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 Acantkodrilus 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 (GAKMAN, 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 j ust beneath the epidermis ; in the clitellar region the duct lies 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-ducts 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 



