quire a careful removal, bit by
bit, before the contained follicles and vessels could be brought into
view."

Like Valenciennes and Van der Hoeven, I have been unable to find any
communication between the four sacs in which the small double clusters
of follicles are contained, and the "pericardium;" and I hold it to be
certain that the other four sets of follicles are not contained in sacs
at all, but lie free in the "pericardium" or posterior chamber.

No notice is here taken of the widely different characters of the
anterior and posterior follicles; and the figure gives both a similar
structure.

Valenciennes ("Nouvelles Recherches sur le Nautile Flambe," 'Archives du
Museum,' ii., 1841) pointed out the existence of three pairs of
apertures opening into the branchial sac, besides the genital and anal
openings; and he affirms that they open into as many closed sacs, which
communicate neither with one another nor with the cavity that contains
the heart. M. Valenciennes indicates the difference in the structure of
the anterior and posterior venous appendages. He seems to me to have
seen something of the part which I have described as the pallio-visceral
ligament; but I cannot clearly comprehend either his figure or his
description.

Van der Hoeven, in his 'Contributions to the Knowledge of the Animal of
_Nautilus pompilius_,' 1850, confirmed the statement of Valenciennes
with regard to the existence of three pairs of apertures; but he showed,
in opposition to him, that one of these pairs of apertures communicated
with the pericardium. The sacs into which the other two pairs open are,
according to this anatomist, blind. In the aperture of the anterior
blind sac he found a concretionary matter which he supposed to contain
uric acid, but chemical analysis did not confirm the supposition. Van
der Hoeven refers to some observations by Vrolik; but as these are in
Dutch, and have not, so far as I can find, been translated into either
French, German, or English, I know not what they may contain.

In his more recent essay, translated in 'Wiegmann's Archiv' for 1857,
under the title of "Beitrag zur Anatomie von _Nautilus pompilius_," Van
der Hoeven states that he has again found hard concretions in the
chamber enclosing the appendage of the anterior branchial artery, and
that these on chemical analysis yielded phosphate of lime and traces of
fat and albumen, but no uric acid.

Mr. Macdonald, in a valuable paper on the anato