8O E. P. CHURCHILL, JR. 



being a phenomenon extraneous to the process of absorption. 

 The latter interpretation seems the more probable as the droplets 

 were not found upon the surface of the cells in nearly all the 

 sections of tissues which had absorbed fat. The sodium may 

 enter the cells with the acid radical and later be separated, or the 

 fatty acid may be split off outside and enter the cell alone. As 

 the fatty acid radical is the constituent of the fat molecule which 

 takes the stain, only that radical could be followed in my prepa- 

 rations. In nearly all cases a fairly definite, though narrow, area 

 lies between the outer ends of the cells and the fat clusters 

 within. This band is the plasma membrane. The fact that no 

 fat droplets could be observed actually in this membrane points 

 to the conclusion that absorption of fat is effected by its solution 

 in the plasma membrane and precipitation within the cell. 



The manner of transportation of the fat within the body 

 deserves mention. The bases of the cells of the intestine are in 

 contact with blood lacunae. Blood vessels traverse the gill 

 filaments. A meshwork of blood lacunae lies in the connective 

 tissue beneath the epithelium of the mantle and foot. A con- 

 siderable amount of fat is taken up and transported by the 

 corpuscles to various parts of the body. Evidence of this is 

 clearest in sections of the intestine and gills (Figs. 1,9, 10, 18 

 and 19), in which corpuscles containing fat are found in close 

 contact with the bases of the epithelial cells. Fat-loaded 

 corpuscles are found in the blood spaces throughout the body 

 of the mussel which had been kept in fat solution for several 

 days. However, sections of the foot and mantle reveal many fat 

 droplets lying immediately beneath the epithelium and clinging 

 to muscle fibers or to the connective tissue instead of being 

 contained in corpuscles (Figs. 4, 7, u and 17). No doubt, 

 besides being transported by corpuscles, fat is thrown directly 

 into the blood stream and carried thus to various parts of the 

 body. In some cases the fat droplets may have become attached 

 to muscle fibers, etc., as was observed in the sections, during the 

 preparation of the tissues. In other cases the attachment may 

 have occurred before the mussel was killed, the tissues to which 

 the fat droplets were adhering being those which were later to 

 oxidize the fat. 



