90 MR. GARNER ON THE ANATOMY OF THE 
Avicula, Lithodomus, Arca, &c. These ganglia give nerves to the branchie, siphons, 
posterior muscle, mantle, &c. The anterior ganglia also give off two twigs, which 
enter the foot and unite into a double ganglion, trom which that organ is supplied with 
nerves. Only a transverse connecting filament exists when there is no foot. The 
posterior and pedal ganglia are totally unconnected with each other. The mouth then 
is surrounded by a ring, of which the part posterior to the situation of the labial ganglia 
upon it, is double. In the Pecten it appears evident that the labial ganglia are com- 
pound. There is no visible sympathetic system, though said to exist by some. 
Digestive System. 
Poli supposes the tricuspid body to regulate the flow of bile into the stomach ; with 
which opinion I coincide, from finding its extremities always in the bile ducts. The 
intestine in molluscous animals gives origin to an abundance of veins, which probably 
act as lacteals. The first part of it is glandular. Sometimes it is not so long as the 
animal, at other times twelve times the length. A ridge is generally seen in it similar 
to what we find in the naked Acephala. This part of the subject has, however, been 
exhausted by Poli; and we pass to the 
Circulating System. 
Bojanus has given a correct description of the circulation in the Anodonta, and has 
shown it to be less simple than it had been described by Cuvier. The result of the 
labours of Bojanus has been this: that the real respiratory organs are two dark-coloured 
spongy bodies, situated at the root of what are generally considered to be the branchie, 
and which are formed by the meeting of many of the veins of the system. I do not 
come to the same conclusion. By means of mercurial injections I find that in the 
Scallop (Pecten maximus) the whole of the venous blood returning from the body does 
not go immediately to the branchie ; but a large portion of it, that of the ovaries, liver, 
and intestine, first circulates in part through the two dark-coloured, venous, secreting 
organs, (lungs of Bojanus,) and in part enters a large sinus or venous dilatation situated 
upon the adductor muscle, which sinus appears to form the branchial artery on each 
side, communicating, however, freely with branches from the secreting organs, these 
last again having a third set of branches entering the branchial artery. The sinus 
above-mentioned, which likewise exists in the Dimyaria, situated under the pericar- 
dium, receives in the Pecten also the veins of the mantle in part, one termination of 
them being directly into the auricles. The branchial arteries are formed by the large 
branch of the sinus, the branches from the secreting organs, and a few small ones from 
the mantle and roots of the branchie. The blood from the branchial veins enters the 
auricles, which have appendages upon them, probably secreting the pericardial liquid. 
The auricles, which in the Oyster are joined together, here communicate by a channel ; 
generally they are quite separate. Two semilunar valves exist at the entry of each 
