The chylific stomach is a simple cylindrical tube, provided at its anterior end with eight (sometimes fewer) cæcal tubes, and opening behind into the intestine. Its muscular coat consists of a loose layer of longitudinal fibres, enclosing annular fibres. Internal to these is a basement membrane, which supports an epithelium consisting of elongate cells which are often clustered into regular eminences, and separated by deep cavities. The epithelium forms no chitinous lining in the chylific stomach or cæcal tubes; and this peculiarity, no doubt, promotes absorption of soluble food in this part of the alimentary canal. Short processes are given off from the free ends of the epithelial cells, as in the intestines of many Mammalia and other animals.

Fig. 65.—Transverse section of tubu­lar pro­long­ation of Giz­zard, with­in the Chyl­ific Stom­ach, part of which is shown at its pro­per dis­tance. R C, re­flect­ed chi­tin­ogenous layer; Tr, tra­cheal tube; M, cross sec­tion of mus­cle; Ep, epi­the­lium of chyl­ific stom­ach. × 100.

Fig. 66.—Epithelium of Chylific Stom­­ach. In the upper figure the di­gest­ive sur­face is in­dent­ed, while in the lower fig­ure it is flat. Both ar­range­ments are com­mon, and may be seen in a single sec­tion. The epi­the­lial buds are shown below, and again below these the annu­lar and longi­tud­inal mus­cles. × 220.

Between the cells a reticulum is often to be seen, especially where the cells have burst; it extends between and among all the elements of the mucous lining, and probably serves, like the very similar structure met with in Mammalian intestines,[124] to absorb and conduct some of the products of digestion. Different epithelial cells may be found in all the stages noticed by Watney—viz., (1) with divided nuclei; (2) small, newly produced cells at the base of the epithelium; (3) short and broad cells, overtopped by the older cells around; (4) dome-shaped masses of young cells, forming “epithelial buds”;[125] (5) full-grown cells, ranging with those on either side, so as to form an unbroken and uniform series. The regeneration of the tissue is thus provided for. The cells come to maturity and burst, when new cells, the product of the epithelial buds, take their place.