344 ALFRED GIBBS BOURNE. 
sac is thick all round the entrance of the sperm-duct, and 
ciliated; it forms, in fact, the “ciliated rosette,’’ which does 
not stand out freely into the cavity of the sac at all: indeed, 
the ciliated epithelium is directly continuous with the rest of 
the epithelium of the sperm-sac. The “ ciliated rosette ” does 
not even present any convolutions of its surface. 
The sperm-duct is much convoluted, and the whole is 
supported and its convolutions bound together by a special 
development of the mesentery, which in other segments 
supports the nephridia. A mass of convolutions lies anterior 
to Septum rx-x, the duct then penetrates the septum, and 
another mass lies posterior to the septum; finally the duct 
runs down and enters the prostate close to the body-wall, and 
at its inner (median) side. The sperm-duct is enormously 
long; I have completely unravelled it under a dissecting 
microscope, and found that when straightened out, without 
stretching, it measures as much as 94 inches. 
I cannot suggest what may be the use of this great length. 
Its walls are ciliated and not glandular, and the spermatozoa 
are not, I believe, built up into spermatophores. 
The wall consists of a layer of slightly flattened cells, ciliated 
upon apparently a portion of their surface only, while outside 
is a thick layer of connective tissue. There is no muscle in 
the wall (figs. 53, 54). 
The sperm-duct opens into the atrium. The shape of the 
atrium varies according as the papilla bearing the male pore 
is protruded or withdrawn, and as the muscles of its own walls 
are contracted or relaxed. When the papilla is protruded the 
atrium is a mere tube; when the papilla is withdrawn, if the 
muscles in the atrial wall are relaxed, the cavity is approxi- 
mately spherical; but if the muscles are contracted the epi- 
thelial lining becomes much plicated and the cavity quite 
irregular, 
The atrial epithelium consists of two kinds of cells—non- 
glandular columnar cells and greatly elongated gland-cells, 
which dip down a great distance below the epithelial layer, 
and are arranged in groups. Hach, however, sends its duct up 
