of the Fishery Boctrd for Scotland. 



43 



which in the oesophagus and upper part of the cardiac sac consists of 

 striped muscular fibres disposed circularly. Under the mucous layer is 

 a well-developed submucous coat. 



The ducts of the tubes or crypts in the cardiac sac are lined by tall, 

 narrow, columnar epithelium, the goblet cells having disappeared. These 

 cells are practically goblet cells. Their upper parts are clear, and are 

 filled with mucus. 



The mucous membrane of the cardiac sac or crop has several well-marked 

 longitudinal folds, running in the long axis of the conical sac. On making 

 sections of it from where it communicates with the pyloric sac downwards 

 into its narrow, funnel-like prolongation, one finds that the secretory parts 

 of the gland tubes gradually become longer, while the gland ducts are more 

 regular and somewhat longer. In the narrow conical end of the crop, the 

 secretory part of the tubes again becomes shorter, the secretory parts being 

 continued for a certain distance in the narrow tube. After a time they 

 disappear, and the continuation of the tube known as the pneumatic 

 duct is lined by a single layer of columnar epithelium. 



PI. I. fig. 3, shows a low power view of a vertical section of the crop 

 about its middle, across one of the longitudinal folds. As a general rule, 

 several gland tubes open into one gland duct. The gland duct is lined 

 by a single layer of columnar epithelial cells, tall and narrow, with their 

 upper ends open, and filled with mucus, while their nuclei are placed near 

 the attached end of the cells. Each secretory part of the gland is simply a 

 tubular gland, which does not seem to possess a distinct basement membrane, 

 so that its lining secretory epithelium rests directly upon the connective 

 tissue of the mucous membrane. Several tubes open into one duct or 

 crypt, as shown in fig. 3. The relation of the connective tissue of the 

 mucous membrane to the gland cells is shown in fig. 4, which represents 

 a section across one of the longitudinal folds of the crop. The mucous 

 coat (sm) sends up thin lamellae (11) of connective tissue between the 

 gland cells (g), and thus forms a limiting membrane and sustentacular 

 tissue. Fig. 5 shows a low power view of a horizontal section of the cardiac 

 sac through the secretory part of the glands. The rounded spaces repre- 

 sent the divided glands, and the cells lining them are not represented. 

 The cells lining the secretory part of the gland form a single row of poly- 

 gonal or cubical cells. They vary somewhat in shape, as is shown in 

 PI. II. fig. 6, which represents several of these cells isolated. As already 

 mentioned, they are polygonal or cubical, but there are many variations 

 from this type ; some have distinct processes (fig. 6). They are arranged 

 one upon the other, and abut closely upon each other, so that neces- 

 sarily their shape must vary. In PI. II. fig. 3, which shows a 'scheme' 

 of such a gastric gland, some of the cells are seen to slant upwards, and 

 to lean upon their neighbour in an imbricate manner. The processes 

 from some of these cells dip in between one cell and the connective tissue 

 outside it. Each cell is usually distinctly granular in appearance, and 

 contains a well-marked, not very large nucleus. Not unfrequently cells 

 containing two nuclei are to be found (fig. 6). I did not discover any 

 distinct cell-wall in these cells. The granular protoplasm certainly differs 

 in different herrings; but my observations have not been sufficiently 

 extensive to enable me to say whether these cells undergo the same 

 appearances during activity and repose as are presented by the ' outer ' 

 cells of the mammalian stomach. The protoplasm sometimes contains a 

 few globules of oil (fig. 6 b), whose presence is readily revealed by osmic 

 acid. 



I found that these cells resisted the action of a dissociating agent, such 

 as potassium sulphocyanide, for a longer time than the columnar epi- 

 thelium lining the crypts. 



