DISTRIBUTION OF SUBCUTANEOUS VESSELS IN GANOIDS 99 



with what is designated as the anterior Jac /a I lymphatic trunk 

 (Fig, ly J^.L.T.{i)). A cut through the spiracle region near the 

 termination of hyo-opercularis trunk in the sinus shows that this 

 canal is accompanied, more profundously, by a corresponding 

 hyo-opercularis artery and vein. All of these vessels are en- 

 closed in a fatty connective tissue, and even in uninjected spec- 

 imens they are readily distinguishable. The lymphatic trunk is 

 the most superficial and has by far the greatest caliber ; no dis- 

 tinct walls were visible to the eye, and it appeared to be simply 

 a regular cavity in the connective tissue, that increased in den- 

 sity in the neighborhood of the canal. A little mesad comes 

 the vein, having visible walls, but with a caliber hardly half 

 that of the lymphatic trunk. The artery, which is by far the 

 smallest of the three, is some little deeper, and is characterized 

 by very thick and well-defined walls. A short distance behind 

 the anterior bend the hyo-opercularis trunk receives a large 

 dorsal branch (Fig. 4, IIyo.O.L.T.{i))y which takes its origin 

 from the outer dorsal surface of the retractor hyomandibularis 

 muscle. At this point the hyo-opercularis artery and vein follow 

 the hyomandibular rather than the lymphatic trunk, yet each 

 sends off a superficial branch (Fig. 4, Hyo.O.A.{i) and 

 Hyo.O. F.(i)) that crosses mesad of the lymphatic trunk, and 

 which separates into two branches that follow the main hyo- 

 opercularis lymphatic trunk and its dorsal branch. So that in 

 this region, each lymphatic canal is accompanied by an artery 

 and a vein. 



Figures 24 to 26 represent microscopic sections of the hyo- 

 opercularis lymphatic trunk, artery and vein. Except for the 

 papilla. Fig. 24, P., in the lymphatic trunk, there is but little 

 difference between the structure of the lymphatic trunk and the 

 vein, and both resemble the jugular and the cephalic lymphatic 

 canal. When the hyo-opercularis lymphatic trunk was slit in a 

 living specimen it was found to be practically empty, and sec- 

 tions show it to be almost destitute of corpuscles. Fig. 24 

 is taken from a very favorable section, and some of the few 

 corpuscles portrayed here may have been shaken out from the 

 meshes of the walls during the process of staining, but as the 

 section stands it shows that the white corpuscles far exceed the 



