The surface epithelium presents, at first, a stratified appearance, but soon becomes a single layer with nuclei approximately in the center of the cells. The stomach glands are formed from round granular cells lying at the base of the surface epithelium. These round cells divide and multiply, forming around a central lumen, while at the same time causing an insinking of the epithelium of the surface to form the excretory duct, by lateral displacement of the surface cells. These then become united—forming at their junction the neck of the gland. So far all three forms agree. But in the pig the epithelial cells multiply and project into the cavity of the stomach to form ridges, supported by mesodermic outgrowths. On these ridges and in the pits between them are found the glands just described. They are lengthened by a further outgrowth of the epithelial cells about their lumen, also supported by connective tissue cores, and a slight downgrowth of the gland proper into the connective tissue beneath. In this way the excretory ducts are formed secondarily in the pig. These round or " ovoid " cells are not characteristic of any one region, but are found over the entire surface of the stomach in all three cases, wherever glands are to be formed. They are specialized very early, as they may be seen in Desmognathus and Amblystoma before the whole stomach is yet fully formed.