80 Swale Vincent and F. D. Thompson, 



Acipenser ruhkundus. lu this species no obvious pancreas was 

 visible to the naked eye. There were whitish masses along the portal 

 vein, and the same in the liver. On microscopical examination, the 

 intrahepatic pancreas is seen to be confined to the region where the 

 portal vein enters the organ, and the zymogenous tissue extends for 

 some distance beyond the limits of the liver, invaded in the infra- 

 hepatic region, and along the portal vein by masses of a haemolymph 

 or splenic nature. 



The zymogenous tissue is accompanied throughout by abundant 

 typical islets of Langerhans. In some places the branching acini form 

 a fairly regular network, with the interspaces occupied by islet tissue, 

 which appears to have practically the same structure as in mammals. 



Again, and perhaps more clearly than in any animal we have 

 examined, we find all stages of transition between islet and zymo- 

 genous tissue. In some parts of the section the zymogenous tubules 

 have their cells distinctly vacuolated, the area of darkly stained 

 protoplasm being reduced to a variable extent by these vacuoles and 

 the edges of the acini having a jagged outline, presenting all the ap- 

 pearances of an invasion of zymogenous tubules by islet tissue. 



Scarcely any of the islets have a clearly defined outline when 

 looked at under the high power. In some regions the islet tissue is 

 invaded by adenoid tissue, and the secreting acini are separated by 

 the same. 



Tlie zymogenous tubules have their structure very beautifully 

 shown, centro-acinar cells are common and occasional darkly-staining 

 (bathychrome) cells among the zymogenous elements are conspicuous. 



Amia calva. The anatomy of the pancreas in the specimen we 

 have examined differs from that in Acipenser in as much as a distinct 

 pancreas could be seen in the first loop of the intestine. On slicing 

 the liver whitish specks are seen. 



acini nearly all the cells appear globular in l'orni, and ol' 1 hose "[lobular cells flioic 

 arc two distinct, varieties, lightly staining and darkly-staining. Occasionally tlicic 

 may be small grouijs of each kind of cidi, and in some places no trace of an 

 alveolar anangenicnt can 1»! detected. Here and there, in outstanding portions of 

 llie coiMK'ctivc tissue, may be seen some of Illese dark or light s|iherical cells, 

 sepaiatcil from (lie r." I ol lln' miicI in;- tissue. 



