G12 R. J. HARVEY GIBSON ON THE 



follicles, and is lined by nucleated squames. Apparently the liver tubules open 

 into a single lobular duct, which passes between the irregular lobes into which 

 the liver is divided. There does not appear to be a common bile duct. 



The stomach proper is a large sac, with a very thin non-glandular wall. The 

 epithelium is often ridged, but the arrangement of the ridges is not constant. 

 The epithelium is very beautiful columnar, ciliated two or three layers deep. 

 The wall is composed of the usual muscle (non-striated) and connective tissue. 

 There are abundant blood spaces in the gastric wall. 



The entire alimentary canal is lined throughout by columnar ciliated 

 epithelium one layer deep, but with young cells inserted between the bases of 

 the superficial large cells. The alimentary canal has, in various parts, the 

 power of secreting in its interior a whitish rod. The nature of that structure 

 will be discussed in the physiological section, with the subject of secretion 

 generally. 



The rectum is often ridged and papillose, in a manner similar to the rectal 

 papilla. The muscle is circularly arranged, and the faeces escape in masses 

 more or less like strings of beads. The cilia of the alimentary canal must be 

 eminently useful in preventing obstruction in the course of a canal of such 

 length. 



The rectal papilla, which projects a variable distance from the anterior 

 edge of the visceral mass on the right shoulder, is composed of a thick layer of 

 circularly-arranged muscle fibres, thrown internally into ridges and papillae, 

 the whole interior being covered by columnar ciliated epithelium. The cilia 

 are very long, and the cells very distinct and perfect. They are arranged in a 

 single layer. The papillae are in most cases compound, and they, assisted by 

 the cilia, no doubt prevent the entrance of infusoria and other small creatures 

 into the rectum. 



The alimentary canal and its connected glands have received less attention 

 than any other part of the animal. With the exception of Cuvier (loc. cit.) no 

 one has clone anything towards unravelling the apparently endless coils in 

 which the intestine lies. The dissection is attended with great difficulty, not 

 only on account of the extreme tenderness of the intestinal walls, but also on 

 account of the intricate way in which the coils are intertwined, and the inti- 

 mate connection subsisting between them and the liver, right kidney, and con- 

 nective tissue supporting these organs. Out of over a score of limpets, which 

 the author dissected with a view to the untwining of the alimentary canal, he 

 was successful in only one case ; and it measured over 14 inches in length, the 

 antero-posterior diameter of the animal itself being 2\ inches. Cuvier's figure 

 errs in showing far fewer coils than there really are ; he excuses himself by 

 saying that the directions in which it twists are " assez inutiles a ddcrire ! 

 The stomach also is inaccurately drawn. The buccal mass, its cartilages and 



