Studies on Earthworms. - Journal of Cell Science

260 WILMAM BLAXLAND BBNHAM.
The sperm duct in Earthworms opens internally by a funnel,
or " ciliated rosette." Usually the sperm duct, which is single
at the external pore, becomes double anteriorly, and ends in a
ciliated rosette beneath each seminal reservoir situated in the
same somite; this ciliated rosette is usually enclosed in the
reservoir, and though Perrier describes it as sometimes free,
e.g. in Perichseta Houlleti, yet it is probably so only in
the immature worm.
Only in one case, Pontodriltis Marionis, are the ciliated
rosettes in front of the seminal reservoirs, being here in somites
x, xi, whilst the reservoirs are in somites xi, xn. Another
variation comes about by the presence of four separate sperm
ducts, each with its external pore, as in Acanthodrilus and
Moniligaster. In Anteus no sperm ducts are known, and
the nephridia of the clitellar region are supposed by Perrier
to function as sperm ducts.
Accessory Organs.—It is only in a few genera that the
sperm duct is without a gland or enlarged portion near the
pore, e. g. Lumbricus, amongst the Anteclitelliani, Urochseta
[as well asMicrochseta, and other forms that I shall
describe later on], amongst the Intraclitelliani.
In Titanus the sperm duct opens into an enlarged, flat,
muscular sac, which does not seem capable of protrusion.
There is no gland, or " prostate " as it is usually called.
In most forms, whose setas have been examined, it is found
that those on the somite at which the male pore opens are more
or less modified. Thus, in Lumbricus they are slightly
modified; in Rhinodrilus they are elongated and ornamented,
as they are also in Urochseta.
In Acanthodrilus this modification is carried further. At
each of the four male pores is a bundle of setse, usually
recurved, enclosed in a sac opening close to the male pore, and
the distal portion of the doubtful prostate is muscular, and probably
protrusible. The most complete " penis" is found in
Eudrilus, where a strong, recurved chitinous hook is enclosed
in a spherical sac on each side of somite xvn, where the male
pore opens. Opening into this sac, besides the sperm duct is an