108 T. H. JOHNSTON. 



consequently there are two testicular fields each containing 

 from forty to forty-five testes, whilst the middle of the 

 segment is usually free from them (fig. 4). The cavity of 

 each testis is continuous with a delicate vas efferens. The 

 vasa efferentia ultimately unite to form the large vas 

 deferens, a thickwalled, muscular structure, at first not 

 coiled, but later becoming a greatly convoluted tube lying 

 immediately internally to the cirrus sac and situated 

 medianly in the medulla just behind the middle of the seg- 

 ment. It becomes very considerably distended by the 

 sexual products contained within it. In well stained pre- 

 parations it appears as a conspicuous organ. It enters the 

 cirrus sac, within which there may be a few more convolu- 

 tions. There is no distinct enlargement representing a 

 vesicula seminalis. 



The cirrus sac is a pyriform body, the narrow end of 

 which is directed laterally towards the genital pore. The 

 walls are thick and possess muscular fibres. In no case 

 was an everted cirrus seen. If eversion is possible, it 

 must be small. There does not appear to be any spines 

 along the end parts of the male duct (fig. 5). 



The ovary is a large paired gland situated at the posterior 

 end of the segment and lying behind the testicular fields. 

 The gland lies somewhat nearer the ventral surface. It 

 consists of a rather large stem or bridge of tissue connect- 

 ing the two glandular parts, and representing a very much 

 enlarged oviduct from which the fairly wide short common 

 oviduct arises to pass backwards to join the fertilising 

 duct. Each glandular portion is made up of a number of 

 blind, more or less dichotomously branching tubes. In 

 some of the older segments the dichotomy is not so recog- 

 nisable. 



The vagina is a well marked duct whose external open- 

 ing is, in most cases, just posterior to the cirrus. It 



