GASTKIC GIANI3S OF THE MARSUPIALIA. 9 



Beaver, except in the arrangement of its openings on the internal 

 surface of the stomach, is not dissimilar from the structures 

 I have described in the Koala and Wombat. In each case 

 the cavity of the stomach is prolonged by means of a variable 

 number of evaginations into short tubular extensions vphich, 

 branching frequently, end in series of tubules which do not anas- 

 tomose but end blindly. The mucous membrane covering the 

 general surface of the stomach is prolonged without interruption 

 into, and forms the walls of, these systems of branching cavities. 

 But whereas in Phascolomys the ramifications of the proximal 

 portions of the evaginations are comparatively simple, the 

 terminal portions short, the branches few, and the lumen a con- 

 tracted one, in Phascolarctus each separate evagination forms a 

 very complex system of tubules communicating with the stomach, 

 which simulate the form of a true raceniose gland. The ter- 

 minal portions are relatively long and their lumina conspicuous. 

 The primary gland tubules making up the gastric epithelium of 

 the gland in both cases are cardiac glands similar to those found 

 on the cardiac portion of the stomach and contain parietal cells. 

 In Phascolomys these glands (PI. 1. fig. 5) form a close-set 

 series of straight unbranched tubules, in length about 0"56 mm., 

 in which parietal cells extend from near the neck to the base 

 of the gland, although they are rather concentrated at the 

 middle of the tubule; while in Phascolarctus each gland (PI. 1. 

 fig. 6), which is about 0'3 mm. in length, consists of a terminal 

 neck portion, lined with columnar or cubical cells (<?«.), which 

 branches several times, forming a series of long tubules opening 

 through a common orifice at the lumen of the gastric-gland 

 involution. As in Pliascolomys and the Beaver, the gland contains 

 both central (c«.) and parietal (c/>,) cells. 



Only the mucosa and muscnlaris mucosae of the various coats 

 of the stomach take part in the formation of the gastric gland. 

 Submucosa and muscularis are only passively affected. In 

 Phascolarctus the musculature over the thickened area is the 

 layer consisting of outer longitudinally and inner transversely 

 disposed fibres, which is characteristic of the other parts of the 

 stomach. But in P^asco/o???^/« the musculature consists almost 

 entirely of bundles of striated fibres ; and the division of these 

 into external longitudinal and internal transverse layers is not 

 so evident as in the case of Phascolarctus, most of the bundles 

 pursuing a more or less oblique course. 



