SEA-FISHERIES LABORATORY. 95 
wall of the testis are isolated from each other, and are 
supported only by a loose connective tissue stroma. The 
Vas deferens leaves the testis from the right anterior 
border of the latter. Of vasa efferentia I can find 
no trace, though these vessels are most difficult to follow 
in serial sections, and they may possibly be contained 
among the tissue called a stroma. But it is more likely 
that the ripe spermatozoa are dehisced into the general 
cavity of the testis, and so find their way into the vas 
deferens. The latter vessel runs forward to the right of 
the ovary and uterus, between the latter organs and the 
right intestinal ramus. Near the posterior margin of the 
cirrus sac the vas deferens becomes convoluted. It is a 
fairly wide vessel, which is everywhere filled with 
spermatozoa. There is no vesicula seminalis or other 
enlargement on the course of the vas deferens. 
Cirrus and Cirrus Sac. 
The cirrus sac is the most anterior of the three 
organs seen behind the pharynx. It is a large, thick- 
walled vesicle, pointed anteriorly in horizontal sections, 
and egg-shaped in longitudinal sections, with the pointed 
end ventral. Its wall is strongly muscular, and consists 
of two series of fibres, circular fibres running parallel to 
the horizontal plane of the worm, and completely round 
the sac; and longitudinal fibres, which originate in a 
cuticularised part of the wall of the sac at its ventral! 
extremity, and run round it in a direction parallel to its 
axis. Both series of fibres are represented in fig. 2, which 
is a section of the cirrus sac taken at right angles to its 
principal axis. In this figure they are represented by 
the dots, while the circular fibres are represented by the 
concentric lines. Other fibres, muscular and tendinous, 
pass out from the wall of the sac, and. are attached to the 
