201 



This species is distinguished from U. lephirus Richardson, (l)by the reduced 

 number and larger size of the vomerine teeth, (^).) by the widely-separated gill- 

 openings, (3) by the increased distance from the gill-opening of the dorsal fin. 



The microscopic structure of the wail of the stomach of Uroconger vicinus. 



The stomach has a lining membrane of two diiferent kinds : in the anterior 

 half the mucous membrane is of an almost horny hardness ; in the posterior half 

 it is soft and glandular ; and the transition between the two is abrupt. 



In vertical longitudinal sections of the stomach-wall, carried through the 

 abrupt line of demarcation between the two different regions of mucotis mem- 

 brane, examined under the microscope, the following structure is seen : — 



(1) Common to both regions of the stomach : (a) an external thin fibrous coat, 

 one-fortieth to one-sixth of a millimetre thick, with many longitudinal bundles 

 of muscular fibres and large blood-vessels ; (Jj) a very compact thin coat of trans- 

 verse muscular fibres, about one-eighth of a millimetre thick ; (c) another very 

 compact layer of longitudinal muscular fibres, about one-seventh of a millimetre 

 thick ; (d) a very thick (^-Ig millimetre) submucous coat made up of a loose 

 mesh-work of branching and anastomosing small-nucleated cells, the meshes be- 

 ing filled with lymphoid cells ; this coat also contains many blood-vessels, which 

 frequently traverse in their course large, compact, sharply-circumscribed nodules 

 of lymphoid tissue, and a great many branching pigment-cells. 



(2) The mucous membrane of the anterior part, which is about one-eighth of a 

 millimetre thick, appears at first like a superficial layer of pure fibrous tissue ; 

 but good sections show that it consists of a stratified epithelium with its consti- 

 tuent cells compressed somewhat as in the horny layer of the human epidermis. 

 These compressed (horny) cells, however, are not flattened into plates to form a 

 smooth surface, but are angularly concreted to form a broken rough surface. 

 Beneath the superficial horny layer are several rows of cells of which the granu- 

 lar protoplasm seems to be fused into a solid mass, leaving only the nuclei dis- 

 tinct ; and beneath this again comes fibrous tissue gradually passing into the loose 

 submucosa. 



(3) The boundarij-line between the anterior horny mucosa and the posterior 

 soft mucosa is very abrupt, and in every section there is seen a conspicuous 

 thickening of the submucous coat at the expense of both the mucous and the 

 muscular coats. The mucous coat is made up of the compact ramifications of 

 an acino-tubular gland lined with granular, large-nucleated, cubical epithelium. 



(4) The mucous membrane of the posterior part, which is rather over one- 

 fourth of a millimetre thick, is formed entirely of long tubular glands packed 

 close together, side by side, at right angles to the surface. These glands, which 

 much resemble mammalian gastric glands, are lined with a granular cubical 



26 



