304 W. BLAXLAND BENHAM. 
prostatiferous worms, viz. (1) a subglobular sac with a short, 
thick, muscular duct opening externally on the anterior edge 
of the segment; and (2) a conspicuous, curved, cylindrical, 
listening diverticulum or appendix, which lies in the segment 
in front of that containing the main sac, with the neck of 
which it communicates. The spermathece lie in Somites vi1t 
and 1x, so that the appendices are in Somites vir and vi11 
respectively. 
Repeated observations have shown that in spermathece 
formed on this plan the sac does not contain spermatozoa, 
which are, as Beddard was the first to point out, found only 
in the diverticulum. This is, on the whole, true in this case 
too, although in sections through the organs I detected a few 
spermatozoa in the neck of one of the spermathece (Pl. XVI, 
fig. 31). 
The microscopic structure of the spermatheca is illustrated 
by figs. 81 and 32. The former, which is combined from two 
or three of a series of longitudinal sections, represents the 
general relation of sac to appendix, and the position of the 
cells which are shown enlarged in fig. 32. The lining cells of 
the sac itself are very much taller than those of the appendix, 
and of slightly different structure when fully developed. 
The appendix has, outside the epithelium, a thick muscular 
coat (mus.). This is absent in the wall of sac, except around 
the neck. The muscle fibres are continuous with the circular 
coat (c. mus.) of the body-wall, which is here very strongly 
developed. 
The cavity of the sac contains some granular matter (2), 
which is produced by the epithelial cells (fig. 32 5), together 
with a few spermatozoa (spoa.). Hach cell is columnar, with an 
oval nucleus near its inner end. The rest of the cell is occupied 
by a finely spherular or granular secretion (v). It appears that 
when the cells have reached a maximum of activity the free 
end projects into the lumen of the sac and discharges its 
contents, leaving then a vacuole or space near this free end 
(as at m.). It then probably shrinks, and gradually elongates 
again as renewed activity commences. The nucleus is only 
