No. 2.] ENTERON OF AMERICAN GANOIDS. 413 



glands. The ental tunic of the peptic glands is composed of 

 large rounded cells which impart an irregular bulging form to 

 the surrounding tunic; the pyloric or mucous glands are lined 

 by small prismatic cells which do not reach to the center of 

 their cavity. 



One of the most important contributions that appeared dur- 

 ing this period was an article by Edinger (18), in 1877, upon 

 the mucous membrane of fishes. He says that the gastric 

 glands appear phylogenetically first in the class fishes — the 

 Selachians. Consequently the older vertebrates, like the in- 

 vertebrates, have no specially differentiated portion of the ali- 

 mentary tract for the purpose of digesting fixed bodies, albumen 

 substances, etc. As to the presence of a stomach in the Dip- 

 noans he is in considerable doubt, but seems to think it rather 

 doubtful if they possess one. Hyrtl, he says, could find no 

 trace of gland openings in the stomach of Lepidosiren para- 

 doxa. In Protopterus, Parker (47) says: "The whole of the 

 mucous membrane of the stomach and intestine is perfectly 

 smooth, and there is no indication of any differentiated gastric 

 or intestinal glands. Cilia are present on the epithelium 

 throughout the stomach and intestine." Among the Teleosts, 

 according to Edinger (18), there are several that have no 

 stomach glands. They are absent in Cobitis fossilis, Gasteros- 

 teus pungitius. Tinea vulgaris, Abranus barbio; according to 

 Rathke (53), they are wanting in Blennius ocellatus and Sangui- 

 nalentus, Gobius melanostomus, Cyprinus chrysophrasius, and 

 Atherina Boyeri. Probably they fail also in Balistes. 



In all these there is found a single somewhat granular cylin- 

 drical epithelium without beaker-cells. In such animals diges- 

 tion must be performed, in part at least, by an intestinal 

 secretion. The gastric glands have probably developed from 

 the ordinary insinking of the alimentary epithelium. Their 

 ontogenesis in the higher vertebrates as well as in those of 

 lower rank indicates the above mode of formation, as shown 

 by KoUiker, Barth, and Laskowsky. In Mammals, Birds, and 

 the Batrachians it has been proved that the epithelium of the 

 stomach glands, at an early stage of their development, is uni- 

 form throughout, and only at a later period are those cells 



