74 E. P. CHURCHILL, JR. 



ing the fat present; and in (&) the cross section of the corre- 

 sponding part of the mussel which had been kept in the fat 

 solution. In the latter the liver cells are seen to be heavily 

 loaded with fat, in some cases practically filled with it. A very 

 great abundance of fat was found throughout the liver cells in all 

 sections of this mussel. 



Figs. 9, 10, and n, PI. I., are drawings made from the sections 

 of the epithelial cells, respectively, of the intestine, of a gill fila- 

 ment and of the side of the mantle next to the body, of the 

 specimen of A . imbecillis which had been kept in the fat solution 

 for 10 days. They represent as accurately as could be drawn 

 with the camera lucida the relative amount and arrangement of 

 the fat droplets. Many corpuscles containing fat were found 

 in the blood lacunse immediately outside of the cells of the intes- 

 tine. Some of these corpuscles were lying at the bases of the 

 cells as shown in Fig. 9. Corpuscles containing fat were also 

 found in nearly all blood vessels of the gill filaments. Many 

 such corpuscles were in the position shown in Fig. 10, that is, 

 close against the bases of the cells of the filament. In the mantle 

 fewer corpuscles were seen. Here the fat was found adhering to 

 muscle fibers and strands of connective tissue. 



Figs. 12 and 13, PI. III., represent mesenchyme cells and blood 

 corpuscles of the mussel which had been kept in the fat solution 

 and of the control individual respectively. In these sections may 

 be observed the relation of the fat droplets to the tissues of the 

 areas occupied by mesenchyme cells, which are especially 

 numerous in the dorsal part of the body of the mussel. Fat was 

 found scattered quite thickly throughout such regions in the 

 case of the animal which had been in the solution. 



The gill of an adult specimen of Quadrula ebena was sectioned 

 immediately after it had been taken from the river. Fig. 14, 

 PL I., represents the relative amount of fat found in its gill 

 filaments. Somewhat more fat appeared in these sections than 

 in those prepared from the tissues of the control mussels which 

 had been kept in filtered water for 10 or 15 days but a very much 

 smaller quantity was found than in the mussels which had been 

 kept in fat solution. 



The mussels which had been kept in the fat solution that had 



