96 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
adjacent ventral integument: these hold the organ in 
position. 
The cirrus sac contains the intromittent organ— 
cirrus or penis. The vas deferens pierces the right wall of 
the sac, and then runs ventrally as a tube of restricted 
diameter. Near the ventral border of the sac it turns 
[An ferior } 
Ductus e 2 jaculatorius 
Giese 




== Nee 
BY 


-— Ss ---— fe 
. 
N\ Cirrus sheath 

deferens == =f 
Bulb us ejaculalorius 
dd (Po Sterior) 
Fia. 2. Section of the cirrus sac passing 
transversely to its long axis. 
round to the anterior wall, and then runs dorsally and 
posteriorly (Pl. I and text-fig. 3), enlarging con- 
siderably in diameter and lumen, and constituting a 
seminal reservoir. Near the posterior border of the sac it 
opens into the bulbus ejaculatorius. This is a cylindrical 
body, rounded at either end, and lying in the posterior 
part of the cirrus sac, roughly parallel to the axis of the 
latter. The vas deferens enters it on its antero-dorsal 
margin, and the wall of the vessel now changes in 
character, becoming more cuticular in appearance. The 
wall of the bulbus is made up of fibres which appear to be 
muscular, but nevertheless have not the precise appearance 
of such. They run radially, being inserted at either 
extremity into the structureless membranes which form 
