nvariably lodged the sperm.

The spermathecae are usually paired structures, one pair to each of
the segments where they occur. In many _Geoscolicidae_, however, and
certain _Lumbricidae_ and _Perichaetidae_, there are several, even a
large number, of pairs of very small spermathecae to each of the
segments which contain them.

In the _Eudrilidae_ there are spermathecae of different morphological
value. In figs. 12 and 13 are shown the spermathecae of the genera
_Hyperiodrilus_ and _Heliodrilus_, which are simple sacs ending
blindly as in other earthworms, but of which there is only one median
opening in the thirteenth segment or in the eleventh. In _Heliodrilus_
the blind extremity of the spermatheca is enclosed in a coelomic sac
which is in connexion with the sacs envolving the ovaries and
oviducts. In _Hyperiodrilus_ the whole spermatheca is thus included in
a corresponding sac, which is of great extent. In such other genera of
the family as have been examined, the true spermatheca has entirely
disappeared, and the sac which contains it in _Hyperiodrilus_ alone
remains. This sac has been already referred to as a coelomoduct. Its
orifice on to the exterior is formed by an involution (as it appears)
of the epidermis, and that it performs the function of a spermatheca
is shown by its containing spermatozoa, or, in _Stuhlmannia_, a
spermatophore. In _Polytoreutus_, also, spermatophores have been found
in these spermathecal sacs. We have thus the replacement of a
spermatheca, corresponding to those of the remaining families of
Oligochaeta, and derived, as is believed, from the epidermis, by a
structure performing the same function, but derived from the
mesoblastic tissues, and with a cavity which is coelom.

_Alimentary Canal._--The alimentary canal is always a straight tube,
and the anus, save in the genera _Criodrilus_ and _Dero_, is
completely terminal. A buccal cavity, a pharynx, an oesophagus and an
intestine are always distinguishable. Commonly among the terrestrial
forms there is a gizzard, or two gizzards, or a larger number, in the
oesophageal region. There is no armed protrusible pharynx, such as
exists in some other Chaetopods. This may be associated with
mud-eating habits; but it is not wholly certain that this is the case;
for in _Chaetogaster_ and _Agriodrilus_, which are predaceous worms,
there is no protrusible pharynx, though in the