COMPARED WITH THAT OF NAUTILUS POMPILIUS. 
281 
with renal glands, to separate from the blood those deleterious principles which must 
otherwise accumulate. In the Nautilus there are no organs to which this function 
can be more justifiably assigned than the numerous glandular follicles appended to 
the vessels which convey the blood from the sinus system to the branchiae ; admit- 
ting also that by altering their capacity they may serve to regulate the amount of 
blood circulating through the respiratory apparatus under those changes of pressure 
which the animal must experience in sinking to great depths and rising in its watery 
element. Mayer suggested that the homologues of these follicles in the higher Ce- 
phalopoda were the emunctories of the urine, and Professor Owen considers it more 
philosophical to conclude that the organs of so important an excretion should be 
present in all the class, than that they should be represented by the ink-gland and 
bag which are peculiar to one order. As the most satisfactory method of arriving 
at a just conclusion, however, I shall leave further argument for the present, and 
describe the minute anatomy of the organs, which may be provisionally called the 
renal follicles of the Nautilus. 
These follicles are subcylindrical in form, somewhat dilated at the free extremity, 
to which is appended a folded and funnel-shaped process of membrane, which ex- 
pands rather suddenly, presenting a jagged and irregular border. They open by a 
smooth and oral or slit-like orifice into the afferent pulmonary vessels, on each of 
which, as Professor Owen has observed, they are disposed in three clusters. 
The outer membrane is smooth and glossy, homogeneous in structure, and 
sprinkled over with minute rounded and transparent bodies, probably the nuclei 
of cells. Beneath this layer flat bundles of fibres, apparently muscular, are trace- 
able here and there, principally disposed in a longitudinal direction, and sometimes 
branched. 
The lining membrane consists of a loose epithelial pavement, in many respects 
similar to that of the uriniferous tubules of the higher animals ; the cells containing, 
besides the nuclei, numerous minute oil-globules, or a substance much resembling 
concrete fatty matter. 
This membrane is thrown up into an infinite number of papillae and corrugations, 
so as to augment the extent of surface considerably. The papillae are more numerous 
at the inner part, or towards the attached end, and a circlet of longitudinally dis- 
posed folds radiate from the bottom of the follicles, in which a number of small pits 
or fenestrations is sometimes visible. The sides of these folds are wrinkled trans- 
versely, 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, there- 
fore, communicates with the exterior through the centre of this process, and the 
aperture is thus guarded by a kind of circular valve, permitting the escape of secreted 
matters, but effectually preventing the entrance of fluid from without. 
