As might be expected there is comparatively little difference between this region of the enteron during hibernation and during the feeding season. The only noticeable difference is in the stratified epithelium; that of the feeding animal not only has less sharp papillæ but has also a much thinner scaly layer of cells. As is seen in the figure of the roof of the mouth during hibernation the scaly cells make up, except on the papillæ, nearly or quite half of the thickness of the epithelium, while in the feeding animal they make up not more than one fourth or one third of the entire epithelium. Very few cells are seen sloughing off as in Figure 40; possibly the act of feeding keeps the superficial scaly cells rubbed off smooth. In the extreme posterior region of the roof of the mouth the epithelium consists of a greater number of layers (though the number is very variable) than in the region shown in Figure 40. In this posterior region, as noted above, glands are found. These glands have the same structure as those described in connection with the posterior region of the tongue. _The Œsophagus._ Sections of the œsophagus were made from two regions, an anterior, half-inch caudad to the pharynx, and a posterior region, half-inch cephalad to the opening of the œsophagus into the stomach (Fig. 35). The general structure of the wall of the œsophagus, as seen under a low magnification, will first be described, after which the minute structure of the epithelium, as seen under high magnification, will be discussed. In the _anterior region_ the usual layers of the vertebrate enteron are present, except, possibly, the muscularis mucosa. The epithelium, to be described later, is, together with the submucosa, thrown into complicated folds; its closely arranged and darkly stained nuclei cause it to stand out in strong contrast to the other tissues of the section (Fig. 41, _e_). The submucosa, _sm_, is of considerable thickness. It is composed of a fairly dense mass of connective tissue, mainly elastic fibers, through which are scattered small blood-vessels, _bv_, and small dark areas, _mb_, that are apparently longitudinal bundles of involuntary muscle fibers. These few and scattered fibers probably represent the muscularis mucosa that is so well developed in the posterior region of the œsophagus. Outside of the mucosa is a thick circular layer of involuntary muscle fibers, _cm_, the fibers being collected into irregular bundles, between which are narrow spaces filled with connective tissue that contains a few small blood-vessels. Surrounding the circular layer is a thinner and less clearly defined layer of longitudinal muscle fibers, _lm_. The muscle bundles are more definite than in the circular layer and are separated from each other by a considerable amount of connective tissue with a few small blood-vessels. [Illustration: