PLATE XIII. 



Fig. 24. Transverse section through the so-called hyo-opercularis lymphatic 

 trunk of a 15-inch Polyodon. The section is taken through a papilla near its 

 surface. In this trunk the white corpuscles, although very scarce, greatly pre- 

 dominate over the red. X 450- Reduced S. 



Fig. 25. Similar section to 24 through the hyo-opercularis artery. X 450- 

 ^Reduced f . 



