establishing a communication between the interior of that tube and
the exterior of the animal."

The foramen here described is easily seen; but, as I have stated, there
are other modes of communication between the so-called pericardium and
the cavity with which the siphuncle communicates, of a far more
extensive nature.

With respect to the pericardium itself, Professor Owen states, "The
peritoneum, after lining the cavity which contains the crop and liver,
and enveloping those viscera, forms two distinct pouches at the bottom
of the pallial sac, in one of which, the left, is contained the gizzard,
and in the other the ovary; anterior to these, and on the ventral aspect
of the liver, is another distinct cavity, of a square shape, which
contains the heart and principal vessels, with the glandular appendages
connected therewith." This is what the author terms the pericardium.

As Van der Hoeven has pointed out, however, the gizzard lies to the
right and the ovary to the left. Moreover, the gizzard is superior to
the ovary, so as only to overlap it a little above; and I can find no
evidence of the existence of such distinct pouches as those described.

Professor Owen states that the branchiae "arise by a common peduncle from
the inner surface of the mantle." My own observations, however, and Van
der Hoeven's figures, of both male and female, lead me to believe that
the peduncles of the branchiae are perfectly distinct from one another.

The follicles of the branchial arteries are thus described in the
"Memoir on the Pearly Nautilus:"--"They are short and pyriform and
closely set together. To each of the branchial arteries are appended
three clusters of these glands, of which one is larger than the united
volume of both the others; and the larger cluster is situated on one
side of the vessel and the two smaller on the opposite side. Each of
these clusters is contained in a membranous receptacle proper to itself,
partitioned off, as it were, from the pericardium, but communicating
with it.... The two canals which form the communication between the
pericardium and the branchial cavity commence at the receptacle of the
lesser cluster attached to the superior branchial arteries, and
terminate at the papillae before mentioned, which are situated at the
roots of the branchiae. The pericardium and these receptacles of the
glands, when first laid open, were found filled with a coagulated
substance so closely compacted as to re