84 THE ANATOMY OF THE NAUTILUS POMPILIUS 
the two divisions of the fifth chamber, the middle, by far the smallest, 
being alone hitherto known. 
A delicate membranous band passes from the whole length of the 
middle line of the rectum to the heart and to the ovary. 
The singular “ pyriform appendage” of the heart lies in the left 
process of the ligament, its anterior edge nearly following the arcuated 
contour of that process. 
The siphuncular process of the mantle was broken in my speci- 
men; but its aperture appeared to communicate quite freely with 
the posterior division of the fifth chamber. 
Four sets of brownish, glandular-looking bodies depend into the 
anterior division of the fifth chamber, from parts of the delicate 
septa dividing this from the four small sacs, corresponding with the 
insertions of the glandular bodies above described. 
In fact, on distending the vena cava with air, it is found that the 
four branchial arteries traverse these septa, and that the appendages 
in question are diverticula of their walls. Consequently the anterior 
wall of each branchial vein is produced into two glandular appen- 
dages, which hang into one of the four smaller sacs, while the posterior 
wall is produced into a single mass of appendages, which hangs into 
the anterior division of the fifth chamber. 
Although, as I believe, the five chambers do not communicate 
directly, all the appendages must nevertheless be equally bathed 
with sea-water, which enters by the apertures of the chambers. 
An impacted yellowish-white concretionary matter filled the 
anterior chamber; and a small quantity of it lay as a fine powder 
at the bottom of the posterior one. In the latter, however, its 
presence might, by possibility, have been accidental. My colleague, 
Dr. Percy, who kindly undertook to examine this substance, informs 
me that he has been unable to detect uric acid in it. The follicular 
appendages of the branchial arteries present remarkable differences 
in their external appearance. The eight which hang into the four 
anterior chambers are similar, slightly festooned, but otherwise 
simple lamella; while the four which depend into the posterior 
chambers are produced into a number of papillary processes. This 
external difference is obvious enough: whether it be accompanied 
by a corresponding discrepancy in minute structure Iam unable to 
say; for I have not as yet been able to arrive at any satisfactory 
results from the microscopic examination of the altered tissues, and, 
as will be seen below, the only observer who has had the opportunity 
of examining the Nautilus in the fresh state has not noted any 
difference of structure in the two sets of follicles. 
