338 PROCEEDINGS OF THE ACADEMY OF [May, 



they are plainly subject to the physical action of the fixing fluid. 

 The fat globules are inside the cells, however, and this must be 

 accepted as evidence of their ability either to appropriate fal in 

 their o^vn metabolism, or to transport it in the metabolism of the 

 body. I have seen nothing which would enable one to decide 

 whether this action is anabolic or katabolic. 



IX. Secretion in the Hepatopancreas. 



Weber (41), who first accurately described the hepatopancreas, re- 

 cognized in its walls four distinct layers : The serous membrane outer- 

 most, the muscular between this and the basement membrane, and 

 finally the epithelial layer. While it is the last named only with 



f ran 



\ '^^s; 











.^ym'g 



Fig. 20. — Section of a single tube of the hepatopancreas of PorcelUo 

 scaber X 120, showing discharge of secretion hj fragmentation and hy 

 rupture of the cell membrane. Frag., fragments of cell passing into the 

 huuen ; Mzym., mature zymogen passing into the lumen by rupture of 

 the cell membrane ; Y.zym., zymogen in a young secreting cell ; Zyvi'g., 

 ZN'mogenesis in a young cell ; Nuc, nucleus of a mature cell. 



which we are specially concerned here, it may be mentioned in pass- 

 ing that Weber's explanation of the form of the tubes by the 

 arrangement of the muscles is important as bearing on the dis- 

 charge of the secretion into the intestine (fig. 1). He shows in 

 his figure that the spiral twist which the tube appears to have 



