REPORT ON THE SPHENISCID^. 



177 



however, the anterior border of the gastric gh\nduhir patch accurately defines the junction 

 of the oesophagus with the stomach. 



The walls of the oesophagus are exceptionally thick. This is due partly to the large 

 development of the muscular coat, which consists of two layers, an external and 

 an internal, but chiefly to the exceptional thickness of the mucous membrane, 

 which is extremely dense and very elastic. Owing to the elasticity of its lining 

 membrane, the oesophagus is capable of enormous dilatation. So much is this the case, 

 that in many specimens of Penguin which had been killed after taking a meal, I found 

 the lower portion of the oesophagus distended with food to such an extent that its 

 diameter almost equalled that of the stomach. On the other hand, when the stomach is 

 empty, the oesophagus, by virtue of the elasticity of its mucous lining, contracts so that 

 its lumen is almost obliterated, and the lining membrane is thrown into the well-defined 

 longitudinal rugae represented in PI. XIII. fig. 4. 



Variations in respect of the CEso^^hagus. 



In all the Penguins which I have examined, the structure and relations of 

 the oesophagus are similar to those above described in Eudyptes chrysocome from 

 Tristan d'Acunha.^ The length of the tube, however, varies in different species. The 

 accompanying table shows the length of the oesophagus in the diflferent species examined, 

 in inches. 



Length of CEsophagus from posteeioe border of Laryngeal Pads to anterior border of 



Proventriculae Gland. 



1 According to Reid (Proc. Zool. Soc, 1835, p. 147), the oesophagus of Aptenodytes patachonica is provided -nitli a 

 " gidar pouch." There was no appearance of any such pouch in any species of Penguin which I examined. I am 

 therefore inclined to consider the " gular pouch " of Reid as nothing else than the upper portion of the oesophagus, which 

 at certain times is found to be packed with undigested food, and thus performs a function similar to that of the 

 " crop " of some birds, at least in so far as it is the receptacle of a quantity of food, which is gradually thereafter 

 transferred to the stomach to undergo digestion. 



^ In Aptenodytes paiacho7nca the oesophagus measures 20 inches in length— Reid, Proc. Zool. Soc, 1835, p. 147. 



(zool. chall. EXP. — PART xviiL- — 1883.) S 23 



