Studies on Earthworms. - Journal of Cell Science

248 WILLIAM BLAXLAND BENHAM.
and extends back as far as the circumpharyngeal nerve commissure.
In Perichseta the pharynx is provided with three pairs of
glands, which open into it, in Moniligaster also there are
small glands in this region. In other cases, e.g. Urochaata,
the first pair of nephridia are much modified, their tube enlarged
and glandular, and the coils are flattened against the
walls of the pharynx so as to become more or less buried in its
muscles, but they have no opening into the pharynx.
The pharynx usually occupies four or five somites, though,
owing to the somewhat infundibulate septa, it appears to
occupy more somites. Lumbricus is often described as
having the pharynx extending through seven somites, whereas
really it occupies only five. InPontodrilusit occupies only
three somites.
The (Esophagus varies much in length, occupying twelve
somites in Lumbricus (including the exceptional " proventriculus"
of this form) whilst in Eudrilus it only extends
through two somites. In Digaster, owing to the presence
of a second gizzard, there is a second oesophagus between
them.
In the greater number of genera there are no glands in this
portion of the alimentary tract; e.g. in Eudrilus, Rhinodrilus,
Acanthrodilus, Digaster, Perionyx, and others.
But in Lumbricus there are three pairs of enlargements
known as " cesophageal" or calciferous glands, two being in
somite xn, the third in somite XIII. The two anterior contain
a milky liquid; the last contains solid carbonate of lime.
Anteus also possesses "ossophageal glands." But it is
in Perichseta that the glandular appendices of the alimentary
tract are most fully developed. Besides the three pairs of
pharyngeal glands there are three different sorts of glands to
the ossophagus. In each of the somites, vi, vn, vm, is a pair
of tufts of glandular tubules. In somite vi there is a pair of
large ovoid, solid-looking glands, each of which opens by a
distinct pore into the (Esophagus, whilst in somite vn there is
a pair of grape-like glands.