AN ACCOUNT OF A RARE ESSEX WORM. 183
lying at the base of the groove which surrounds the mouth, and
a ventral nerve cord, which is visible exteriorly as a light line,
this defining the ventral surface of the creature.
The sexes are distinct, and in adult specimens the ovaries
or testes are easily recognizable lying to the right and left of the
alimentary canal. The reproductive glands are in direct
communication with ducts which serve as oviducts or vasa
deferentia respectively. The ducts open to the exterior, one on
either side of the anus.
Shipley found that specimens of Priapulus died at the end of
two or three weeks' confinement in an aquarium. Two
specimens kept in an aquarium in the Stratford Museum have
survived for nearly two months, whilst a single animal is still
quite healthy after living in Mr. Lambert's aquarium for nine
weeks.
Placed on the surface of the mud Priapulus burrows down-
wards by the protrusion and invagination of the introvert, the
mouth being carried into the body during the latter operation.
The downward progress is very slow, and if coarse sand and small
pieces of grit are mixed with the mud it will not be able to effect
an entrance, let alone bury itself. Further, when it is discovered
in its natural environment one cannot help being struck with
the picture of helplessness it presents by its feeble and futile
attempts to escape from view. Exposed on the surface of the
glutinous mud the only movements made are a slight lowering
and raising of the anterior and posterior regions simultaneously
with a very slow extension and retraction of the introvert. It
remains thus until the introvert can take up a position to strike
into the mud at right angles and so secure a hold.
In conclusion it is worth while recalling that nothing is known
of the embryological and larval stages of this worm, and until
these are studied its position in the animal kingdom cannot be
accurately determined. The Priapuloidea have little in common
with the other orders of the Gephyrea, differing in the structure
of the nervous, excretory and reproductive systems, and agreeing
only in the possession of a sac-like body and a protrusible anterior
end.
The occurrence of Priapulus caudatus in Essex puts the
deciphering of one of many unknown zoological problems within
the scope of members of this club.