A peritoneum envelops all the divisions of the intestinal tract within the abdominal cavity. A broad, well-developed _omentum_ has hitherto been found in _Gobiesox cephalus_ only. _Liver_.--The existence of a liver in _Branchiostoma_ as a long diverticulum of the intestine has been mentioned above. In the Myxinoids the liver is divided into two glandular bodies, an anterior rounded smaller one, and a posterior larger one of an elongate shape. The gall-bladder lies between both, and receives a cystic duct from each of them. In the other fishes the proportionally large liver is a single large gland, from which only now and then small portions are found to be detached. It is either simple, or with a right and left lobe, or with a third lobe in the middle; each lobe may have incisions or subdivisions, which, however, are very inconstant. The liver of fishes is distinguished by the great quantity of fluid fat (oil) which it contains. The gall-bladder is but rarely absent, and attached to the right lobe, or towards the centre; however, in some fishes it is detached from the liver and connected with it by the cystic duct only. The bile may be conveyed by one or more hepatic ducts into a common duct which is continued towards the gall-bladder as _ductus cysticus_, and towards the duodenum as _ductus choledochus_; or some of the hepatic ducts enter directly the gall-bladder, or directly the duodenum, without communicating with the common duct. Individual variations in this respect are of common occurrence. A _pancreas_ has been found hitherto in all Chondropterygians, Acipenser, and many Teleosteans. In the first it is a glandular mass of considerable size behind the stomach, close to the spleen; its duct leads into the duodenum. In the Sturgeons the pancreas is attached to the duodenum, and opens close to the ductus choledochus. In _Silurus glanis_ it is very large, and the ductus choledochus passes through its substance; it is smaller in _Belone_ and _Pleuronectes_, and situated in the mesentery; its duct accompanies the terminal portion of the ductus choledochus. In the Salmon, which possesses a large lobed pancreas, the duct is so intimately connected with the ductus choledochus that both appear externally as a single duct only.