THE ANATOMY OF THE NAUTILUS POMPILIUS 89 
The papilla) are more numerous at the inner part or towards the 
attached end; and a circlet of longitudinally disposed folds radiate 
from the bottom of the follicles, in which a number of small pits or 
fenestrations are sometimes visible. The sides of these folds are 
wrinkled transversely so as to present a median zigzag elevation. 
The funnel-shaped membranous process above noticed is continuous 
with the lining membrane, consisting of an extension of the same 
epithelial pavement; but the cells are somewhat larger and more 
regular in form. The cavity of each follicle, therefore, communicates 
with the exterior through the centre of this process ; and the aper- 
ture is thus guarded by a kind of circular valve, permitting the 
escape of secreted matter, but effectually preventing the entrance of 
fluid from without.” 
In his fig. 9, pl. xv., Mr. Macdonald depicts certain “crystalline 
bodies often occurring within the follicles.” 
From what Mr. Macdonald states, one would be led to conclude 
that all the follicles have the same structure; but I suspect this to be 
an oversight. 
In the second edition of Professor Owen’s “ Lectures on the In- 
vertebrata” (1855), I find no mention of Valenciennes’ discovery of 
the additional four apertures; but the author states that “on each 
side, at the roots of the anterior branchiz, there is a small mamillary 
eminence with a transverse slit, which conducts from the branchial 
cavity to one of the compartments of the pericardium containing two 
clusters of venous glands. There are also two similar, but smaller, 
slits, contiguous to one another, near the root of the posterior branchia 
on each side, which lead to and may admit sea-water into the com- 
partments containing the posterior cluster of the venous follicles.” 
In this work the ovary is not only described, but figured, on the right 
side of the gizzard. The figure, however, rightly places the greater 
part of the ovary below that organ. 
