DISTRIBUTION OF SUBCUTANEOUS VESSELS IN GANOIDS IO7 



From both the lateral and mesal side of the efferent branchial 

 artery, numerous branches, designated as nutrient branchial 

 arteries (Figs. 17 and 20, N.Br.A.} arise to supply the mem- 

 branes and connective tissue, overlying and underlying the 

 efferent branchial artery. Two such branches were sent to the 

 base of each filament. They were found on either side of the 

 efferent filament artery, a little profundus of the lymphatic net- 

 work, but could not be traced much beyond the base of the fila- 

 ment. Many branches were given off to the gillrakers, and 

 forking to follow the dorsal and ventral surfaces of two adjacent 

 rakers, they break up into a fine network in the membrane 

 connecting them (Fig. 17, G.R.N.}. Also very fine arterial 

 twigs as d, Fig. 20, were frequently seen in the region 

 bordering the filaments, but no connections, not even with the 

 aid of a microscope, could be established with the so-called 

 lymphatic network. 



What is designated as the branchial arch artery 1 (Fig. 17, 

 Br.A.A.} approaches the arch from the anterior dorsal corner. 

 Shortly before the arch is reached it bifurcates. A large outer 

 fork (Br.A.A.(i)) is given off to supply the outer surface of the 

 arch, while the inner fork immediately makes a sharp curve to 

 pass to the cephalic margin of the arch, and continues parallel 

 with the lymphatic trunk. It is, however, a more profundus 

 vessel, traveling for a good part of its length in a muscle over- 

 lying the inner surface of the arch. Branches are frequently 

 given off to the muscle and the distal membranes, and they are 

 often accompanied on either side and sometimes nearly sur- 

 rounded by the so-called lymphatics. The caliber of the 

 branchial arch artery and its branches is, however, only minia- 

 ture, when compared with the corresponding lymphatic canals. 



At this point there arises an apparent inconsistency. In all 

 other parts of the head region in Polyodon we have arteries, 

 veins, and lymphatics, running parallel with one another, but in 

 the branchial arch and filaments (not taking the respiratory sys- 

 tem into consideration) only arteries and lymphatics have been 

 described. If peripheral connection had been established be- 



J The source of this artery from the dorsal extremity of the efferent branchial 

 artery has not been worked out as carefully as it should have been. 



