144 T. H. JOHNSTON. 



being part of the cirrus sac. When the organ is fully 

 everted it extends at least 0*3 mm. Even then a consider- 

 able part of the bristled wall still remains within the cirrus, 

 as is shown in fig. 5. In younger segments the organ may 

 be curled at its inner end. The cirrus lies dorsally to the 

 vagina, its opening being just above and in front of the 

 female pore. 



The vagina is an exceptionally wide tube, occasionally 

 twisted, with very well defined walls containing some 

 longitudinal muscles. It courses inwards and backwards 

 to the middle of the segment. Its inner end may be slightly 

 swollen and rounded, but as a rule a receptaculum seminis 

 cannot be distinguished. 



The ovary is a distinctly bilobed, somewhat branched 

 organ lying just behind the midregion of the segment. 

 Though very small at the time when the testes are 

 approaching their full development, it rapidly increases in 

 size and appears to dwindle again very soon. The descrip- 

 tion of the female complex is unfortunately not as complete 

 as I would like, but the parts are very hard to distinguish. 

 The rapid growth of the uterus obscures these parts. 

 Neither oviduct nor shell gland are recognisable. As 

 mentioned above, the developing ovary is encircled by the 

 testes. 



The vitellarium lies near the posterior edge of the seg- 

 ment as a rounded organ. From it there passes forward 

 a delicate vitelline duct which enters the inner end of the 

 vagina, or as it ought perhaps to be called here, the fer- 

 tilising duct, just before it opens into the uterus. 



The uterus appears rather late but it develops very 

 rapidly, becoming filled with eggs and then assuming a 

 simple sac-like form which it retains. When ripe it almost 

 fills the segment, the vagina, cirrus sac and its muscular 

 system however, still persisting. The fertilising duct 



