DISTRIBUTION OF SUBCUTANEOUS VESSELS IN GANOIDS 89 



able to let go of the idea that a fish must have a lymphatic sys- 

 tem ; while he himself is so impressed with the uselessness of 

 such a system to a fish, that it almost appears to him as if it 

 would be hateful in the eyes of the Lord for a fish to possess a 

 lymphatic system. One might equally well apply the same 

 line of reasoning to mammals. 



With Raja clavata Mayer found the lymphatic hearts of Ley- 

 dig and Sappey, or as he calls them sphincters^ very abund- 

 ant ; while with their close relatives they were often absent. He 

 also found them encircling arteries, and hence for these reasons 

 was not willing to attribute the importance to them that Sappey 

 did. 



In the trunk region, in addition to the caudal vein and its inter- 

 costal branches, Mayer notes (pp. 316-337) not fewer than four 

 longitudinal veins that have no counterpart in the arterial sys- 

 tem. They are homologous to the dorsal, ventral, and lateral 

 cutaneous veins of Parker and the corresponding lymphatic 

 trunks of Sappey. In addition to the descriptions given these 

 vessels by these authors, Mayer finds that the laterals not only 

 terminate cephalad in subscapular reservoirs that empty into the 

 cardinal sinuses, but continue cephalad to the orbit, where they 

 send off anastomosing cross branches that also unite with the 

 dorsal vein. Caudad the dorsal vein empties into a lateral and 

 they, at the origin of the tail, unite with the ventrals, which are 

 here paired, and shortly bend dorsad to culminate in the caudal 

 vein. The two forks of the dorsal that encircle the dorsal fins 

 are designated by Mayer as vencB ctrculares, which are said to 

 receive two large branches from each fin. One or two vetia 

 posttca come from the posterior part of the fin, and a vena pro- 

 funda arises from the musculature of the fin. They unite in a 

 small reservoir at the base of the fin, whicTi communicates with 

 the vena circularis. All of the orifices in the reservoir are said 

 to be guarded by valves. Also all of the venous openings into 

 the caudal vein are likewise protected by valves. Certain blood 

 cavities were found in the haemal canal, which may correspond 

 to the haemal lymphatic trunk of the bony fishes. 



Neuville {op. cil.) studied in detail the blood vascular supply of 

 the viscera in Petromyzon marinus and in numerous Selachians. 



