THE ANATOMY OF THE NAUTILUS POMPILIUS 85 
One is naturally led to seek among other mollusks for a structure 
analogous to the vast posterior aquiferous chamber of the Nautilus ; 
and it appears to me that something quite similar is offered by the 
Ascidioida and the Brachiopoda. In both cases, the viscera, inclosed 
within a delicate tissue, project into a large cavity communicating 
freely with the exterior by the cloacal aperture in the one case, and 
by the funnel-shaped channels which have been miscalled “hearts” 
in the other. 
The rudimentary renal organs of the Ascidian are developed in 
the walls of the cavity in question; and an aquiferous chamber of 
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Fic. 1.—Nautilus pompilius. Viewed from the left side and a little behind. 
‘Two of the anterior chambers, and the fifth or posterior chamber, laid open. Natural size. 
a. Shellmuscle. 4. Ovary. c. Intestine. @. Heart. d’. Its pyriform appendage. e. Superior 
anterior chamber; e’. Its follicles. 6 Inferior anterior chamber; /’. Its follicles. 
g. Posterior chamber ; 9g’. Follicles. 4. Cut ends of branchial arteries. z. Termination 
of vena cava. 4%. Pallio-visceral ligament. 
smaller dimensions has the same relation to the kidney in Lamelli- 
branchiata—in Gasteropoda, Heteropoda, Pteropoda, and dibranchiate 
Cephalopoda. But although such is likely enough to be the case, we 
do not know at present that the aquiferous chambers in any of the 
last named mollusks attain an extension similar to that which obtains 
in Nautilus. 
On comparing the observations detailed above with the state- 
ments of previous writers, I find that, in his well-known “ Memoir on 
the Pearly Nautilus” (1832), Professor Owen describes “on each side, 
at the roots of the branchie,” “a small mamillary eminence with a 
