Premnodrilus palustris. 463 



part of XI, where they enter the wall of the anterior end of 

 a long sperm-reservoir which extends backward through six 

 to eight somites. After passing through the muscular layer 

 of this wall the ducts pass between it and the inner epithelium 

 to the posterior end of the reservoir, where they open into 

 its cavity. The anterior part of the reservoir is continued 

 as a much narrowed and often considerably contorted duct, 

 which is continuous with the inner end of a large muscular 

 penial apparatus, the spermiducal pores being situated on 

 the posterior part of the ventral side of IX. 



We can now go a little more into detail in describing the 

 spermiducal structures. As already stated, there are no 

 testes in VIII, although that somite contains a pair of sperm- 

 iducal funnels. The presence of an abundance of sperma- 

 tozoa in the sperm-reservoir and spermathecas and of well- 

 developed ova bears evidence that the animals had at least 

 reached a state of sexual activity, and yet the most careful 

 examination revealed not the slightest trace of testes in 

 VIII. A similar condition of affairs is described by Beddard 

 ('92, p. 196) as existing in Sutroa alpestris, in which species 

 he found spermiducal funnels in IX and X but no trace of 

 testes in the former somite. The smaller and more variable 

 size of the funnels in VIII and the smaller diameter of their 

 ducts — which is only a third of that of the posterior ones- 

 may reasonably be regarded as indicating a degenerate con- 

 dition, and that the complete disappearance of the testes has 

 preceded that of the funnels and ducts. 



Each of the sperm-ducts leading from the anterior funnels 

 bends abruptly down, passing through the testis close to its 

 attachment to the septum. It then turns posteriorly and 

 passes into the extensive mass of muscular tissue surround- 

 ing the ventral part of the penial structure. After emerging 

 from this mass it extends upward for a short distance along- 

 side the muscular investment of the penis, passing along its 

 ental surface, and then extends across to the muscular duct 

 between the penial organ and the sperm-reservoir, which it 

 follows to the latter organ, and, as before stated, passes 

 between its muscular layer and inner epithelial lining, along 



