These pouches or diverticula of the intestine form the so-called pyloric cæca or appendices of these fish. They vary very much in length, diameter and number in different forms.
Thus but a single diverticulum appears in _Polypterus_ and _Ammodytes_ (Fig. 205). _Rhombus maximus_ and _Echelus conger_ (Figs. 112 and 206) have two, and the same number appear in _Lophius piscatorius_ (Fig. 207). Perca has three and the _Pleuronectidæ_ have three to five.
[Illustration: FIG. 205.--Alimentary canal of _Polypterus bichir_. (Columbia University Museum, No. 1823.)]
[Illustration: FIG. 206.--Alimentary tract of _Echelus conger_, Conger eel. Stomach, mid- and end-gut, liver, and spleen. (Columbia University Museum, No. 1430.)]
[Illustration: FIG. 207.--Stomach, duodenum, and pyloric cæca of _Lophius piscatorius_, angler. (Columbia University Museum, No. 1824.)]
Fig. 208 shows the stomach and the beginning of the midgut with four pyloric cæca in _Pleuronectes maculatus_, and Fig. 209 the same parts of this animal in section.
[Illustration: FIG. 208.--_Pleuronectes maculatus_, window-pane. Stomach and mid-gut with pyloric cæca and hepatic duct. (Columbia University Museum, No. 1432.)]
[Illustration: FIG. 209.--_Pleuronectes maculatus_, window-pane. Stomach and mid-gut with pyloric cæca, in section. (Columbia University Museum, No. 1433.)]
[Illustration: FIG. 210.--_Paralichthys dentatus_, summer flounder. Stomach and mid-gut with pyloric cæca and liver. (Columbia University Museum, No. 1431.)]
Fig. 210 shows the stomach and midgut of _Paralichthys dentatus_, the summer flounder, with three well-developed conical pyloric cæca. On the other hand in some forms the number of pyloric appendices is enormously increased, while their caliber diminishes. Thus 191 cæcal appendages are found surrounding the beginning of the midgut in _Scomber scomber_. A well-marked example of prolific development of the pyloric appendages is furnished by the common cod, _Gadus callarias_ (Fig. 211). The appendices are in the natural condition bound together by connective tissue and blood vessels, so as to form a compact organ, resembling a gland (Fig. 211, A), and a similar arrangement is found in _Thynnus vulgaris_ and _alalonga_, _Pelamys_ and _Accipenser_ (Fig. 212).