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ALIMENTARY CANAL: BURROWING. 
The alimentary canal consists of (1) an eversible 
c 
buccal mass and pharynx or “ proboscis” generally of a 
pimish colour in young or middle aged specimens, due 
to the contained blood-vessels, but in old specimens liable 
to become darkly pigmented; (2) a cylindrical, pinkish or 
greenish brown cesophagus, often transversely wrinkled, 
which pierces the three diaphragms, and, just behind the 
level of the last of these, bears a pair of glands; (3) the 
stomach, which has yellow walls on which are numerous 
blood streams, extends from the level of the heart to that 
of the eleventh or twelfth sete, and gradually merges into 
(4) the intestine, which is yellowish brown or dark olive 
green in colour, and extends to the posterior end opening 
at the anus (fig. 23). 
During life the “proboscis” is being constantly 
everted and withdrawn, carrying sand into the cesophagus. 
During eversion the buccal mass is first extruded, this is 
armed with several rows of curved, bluntly pointed, vas- 
cular papille, which in old specimens are capped with 
chitin (figs. 1,3 and4). Then the more globular pharynx 
covered with minute rounded processes is protruded. 
These papille, which are covered by a thin cuticle, have 
an axis containing muscle fibres and connective and 
nervous tissue covered by a columnar epithelium, in which 
numerous mucus-forming cells are present. Among the 
columnar cells there are here and there fine fusiform 
sense-cells, the drawn-out tips of which project into or 
through the cuticle covering the papille. 
The csophagus is a thin-walled, distensible tube, 
which is lined by elongate, columnar cells, among which 
are swollen mucus-forming cells and occasional gland cells 
of other kinds, the latter being more numerous in the 
