Pvn H,i I'UitlS

8 BRACHIOPODA. *
Some Terebralula: which I watched for a long time
seemed, however, to be more active than passive in
feeding. They were incessantly opening and folding
their cirrons arms, and drawing or sncking in, by means
animalcule within its
of the whirlpool thus caused, every
influence. The action reminded me of that of a Bar-
nacle, the only difference being in the position of the
arms, which in Balanus are placed in front, and in
Terebratula on the sides of the animal. Possiblv Cuvier's
notion that the Brachiopods do not differ much from
the Cirripeds was correct, although the relationship be-
tween them may be one of analogy rather than of
affinity. Very lately Dr. Gratiolet has expressed an
opinion that the Brachiopods are allied to the Crustacea
in respect of their vascular system, and not to the
or least of all to the Tunicata. Milne-Ed-
Mollusca,
wards has included them with the Tunicata and Poly-
zoa, in his Class " Molluscoida." Lacaze-Duthiers sepa-
rates them from the Acephala mainly on embryogenic
grounds, remarking that the difference in this respect
between the Brachiopoda and Acephala is as great as
between the latter and the Gasteropoda. In this contro-
verted and unsatisfactory state of our knowledge, it
would seem best to retain them for the present in the
great kingdom of the Mollusca, as a class of coordinate
value with the Conchifera,— the Pteropoda and Gasteropoda
forming another and equally poised group. The
Brachiopoda have certainly some features in common
but
with the Tunicata, as well as with the Conchifera ;
they differ essentially from both in having cirrous arms,
in which latter respect they resemble the Cirripedia.
The perforated structure of their shells agrees with that
of the Balanidce, and also of the Polyzoa. They are con-
fessedly anomalous, and to a certain extent sui generis.