10 ME. JAMES JOHNSTOIS'E ON THE 



The gi'eat development, of striated muscle fibres over the 

 gastric gland seems remarkable, but since the posterior limit of 

 the striated musculature characteristic o£ the upper part of the 

 oesophagus seems to vary in different animals, this extension into 

 the region o£ lesser curvature of the stomach, is probably without 

 any special significance. But it suggests a comparison with the 

 glandular" bulbus ventriculi " oiMyoxus avellanarius — an organ 

 which, though not strictly homologous with, probably belongs to 

 the same category of structures as, the gastric glands o£ the 

 other mammals mentioned, and in which the musculature is a 

 striattd one. This organ was first described by Home (5), 

 who compared it with the gastric gland of the Beaver, with 

 which he found it to correspond " very minutely in its internal 

 strncture." It appears as a bulb-like enlargement o£ the lower 

 portion ofthe oesophagus resting on the stomach, from which it is 

 separated by a deep constriction. The cuticular lining of the 

 oesophagus ceases at its anterior extremity, and is replaced by a 

 very thick layer of glandular epithelium containing glands made 

 up of central and parietal cells. Home describes these glands as 

 having an arrangement similar to those in the glandular pad of 

 the Beaver's stomach. " Each orifice," he says, " exposes three 

 small openings, these again lead to smaller processes, as has been 

 described and delineated in the glandular structure of the Beaver." 

 Leydig (7), speaking of the glandular appendage on the cardiac 

 part of the stomach of Manatus, where a compound tubular 

 gland is found, refers to the " Vormagen " of Myoxus as some- 

 thing similar. Meckel regarded it as a truly avian structure. 

 Toepfer (11), who investigated the structure of this organ, found 

 it to be provided with a thick layer of striated muscle-bundles 

 which are a direct continuation of those found in the upper 

 part of the oesophagus ; and, in a discussion as to its morphological 

 nature, he regards the presence of the epithelium rich in glands as 

 affording a more reliable test of the morphological nature of the 

 organ than the presence of an oesophageal musculature. If the 

 bulbus is gastric and not oesophageal in origin, then the whole 

 stomach of Myoxus — i. e. the true stomach and bulbus ventriculi — 

 is homologous with the simple stomach of Castor provided with a 

 concentration of cardiac glands on the region of its smaller 

 curvature, since in Myoxus such a concentration occurs round the 

 entrance of the oesophagus. 



In the Beaver, as in Phascolomys diudi Phascolarctus, there is the 



