86 THE ANATOMY OF THE NAUTILUS POMP{LIUS 
transverse slit which conducts from the branchial cavity into the 
pericardium. There is, moreover, a foramen at the lower part of the 
cavity (0, pl. 5) permitting the escape of a small vessel; and by the 
side of this vessel a free passage is continued between the gizzard 
and ovary into the membranous tube or siphon that traverses the 
divisions of the shell, thus 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 peri- 
cardium 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 branchie “arise by a common 
peduncle from the inner surface of the mantle.” My own observa- 
tions, however, and Van der Hoeven’s figures, of both male and 
female, lead me to believe that the peduncles of the branchie 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 oppo- 
site side. Each of these clusters is contained in a membranous 
receptacle proper to itself, partitioned off, as it were, from the peri- 
cardium, 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 papilla before men- 
