82 E. P. CHURCHILL. JR. 



EXPLANATIONS OF PLATES. 



All drawings were made with camera lucida; Leitz Oc. No. 4, Obj. No. 6, unless 

 otherwise indicated. The drawings are of sections prepared by the osmic acid 

 method unless otherwise stated. Fat is represented by heavy black dots or areas. 



PLATE I. 



FIG. i. Gill filament of adult Quadrula ebena after remaining in fat solution 

 1 5 days, a, epithelial cells, b, blood vessel, c, blood corpuscles, d, chitinousrods. 



FIG. 2. Gill filament of the control for above figure: mussel had remained in 

 filtered water 15 days, a, b, c, d, same as in Fig. i. 



FIG. 3. Gill filament of adult Quadrula ebena after remaining in fat solution 

 15 days. Frozen section, Sudan III. 



FIG. 8. a, Cross section of liver tubule of juvenile A. imbecillis after remaining 

 in filtered water 10 days, the control, b, Cross section of liver tubule of juvenile 

 A. imbecillis after remaining in fat solution 10 days. 



FIG. 9. Epithelial cells of anterior part of intestine of juv. A. imbecillis after 

 remaining in fat solution 10 days, a, epithelial cells, b, blood corpuscles. 



FIG. 10. Gill filament of juv. A. imbecillis after remaining in fat solution 10 

 days, a, blood corpuscles. 



FIG. ii. Portion of epithelium on side of mantle next to the body of juv. A. im- 

 becillis after remaining in fat solution 10 days. 



FIG. 14. Gill filaments of adult Quadrula ebena sectioned immediately after 

 taken from the river. 



FIG. 15. Portion of gill filament of adult Quadrula ebena after remaining in 

 Sudan stained fat solution 15 days. Black areas represent droplets of pink colored 

 fat. Frozen section. 



