Miscellaneous. 157 
MISCELLANEOUS. 
On some Points in the Anatomy of the Common Mussel (Mytilus edulis). 
By M. A. Sasarrer. 
In the mussel the apparatuses of circulation, respiration, and 
urinary excretion present arrangements which differ in some respects 
from those observed in the Lamellibranchiate Mollusca generally. 
The central apparatus of circulation consists of a heart with two 
auricles, which does not furnish an aorta at its posterior extremity. 
This aorta springs from the anterior aorta at the lower surface of 
the aortic bulb, and passes backward to supply the stomach and in- 
testine. The anterior aorta furnishes the hepatic and tentacular 
arteries and especially the great parallel arteries which are distributed 
over the outer surface of the mantle. 
The return passages of the blood to the heart are very complex, 
and vary according to the organs. On each side of the body there 
is a great vessel, running obliquely from above downwards and from 
the front backwards, which opens directly into the auricle ; this is 
the oblique afferent vein. Its lower extremity opens into a large 
longitudinal cavity, situated at the level of the adherent margin of 
the mantle and composed of two parts, a posterior and an anterior 
longitudinal vein. 
The veins of the mantle are placed on the inner surface. They 
ascend towards the adherent margin of the mantle, and anastomose 
below this margin to form a large, zigzag, horizontal vein. From 
the superior angles of this sinuous trunk spring vertical trunks, which 
soon subdivide into small canals to penetrate into some special organs, 
which I shall describe under the name of platted or frilled organs. 
The blood which has traversed these organs penetrates in part into 
the vascular network of the corpus Bojani, and in part into the 
anterior longitudinal vein. The blood coming from the liver and 
the anterior visceral mass penetrates directly into the corpus Bajani. 
A small portion of the blood from the mantle passes, also directly, 
into the oblique afferent vein, and another portion directly into the 
anterior longitudinal vein. 
The corpus Bojani is far from presenting the characters seen in it 
in most Lamellibranchiate Mollusca. It does not form a clearly 
distinct organ as in these Mollusca; but neither is it entirely com- 
posed, as has been asserted, of plates of Bojanian tissue lining the 
walls of the large veins and auricles. In fact we can distinguish 
in the corpus Bojani of the mussel two different parts—one autono- 
mous, the other dependent on the large veins. The autonomous 
part is anterior, and is to be seen on the lateral portions of the 
liver, in the furrow which separates that organ from the base of the 
branchiz ; it is formed of a series of vertical membranous folds, and 
is of a greenish brown colour. The folds enclose cavities which 
open successively by their superior extremities into a collecting 
canal, the diameter of which increases rapidly from before back- 
wards, and which is exactly within the afferent vessel of the branchia. 
