The ductus cochlearis and the two scalae are filled with fluid.
This it accomplishes by the structures in the ductus cochlearis.
From the ductus venosus there is given off a vein which quickly divides into two branches.
The main trunk is however never completely aborted, as in the embryos of other types, but remains as the ductus venosus Arantii.
The ductus venosus becomes moreover merely a small branch of the vena cava.
In Elasmobranchii the primitive median diverticulum (fig. 421) gives rise to the ductus choledochus.
In Selachians the otocyst remains in the adult open to the exterior by the ductus endolymphaticus.
From the point of junction of anterior and posterior cardinal a large transverse vessel leads to the heart (ductus Cuvieri).
The sinus venosus receives the blood from the great veins (ductus Cuvieri and hepatic veins).
The topographical relation of the head of the pancreas to the ductus choledochus is of clinical importance.