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. 40 WII)lIAM F. ALLEN 



along the iiiterinediate alternate neural spines there pass neural 

 veins, which have identical courses to the corresponding arteries, 

 draining the same regions they supplied, and terminating in the 

 caudal vein. Assuming for a moment the neural lymphatic ves- 

 sels to be neural veins; there would be a neural artery and vein 

 for each alternate neural spine, and two neural veins, having 

 almost identical courses for every intermediate alternate neural 

 spine; thus constituting a very unlikely arrangement. Exactly 

 the same correlation can be shown in connection with the hsemal 

 vessels. 



The following observations to a certain extent favor the suppo- 

 sition that this sysiem is a venous system. — On both sides of 

 the superior hypural bone in Scorpsenichthys there was noted an 

 arterial and a lymphatic system, but no vein was observed coming 

 from that locality, unless the hypural lymphatic vessel also func- 

 tion as a vein. Likewise in Clinocottus the caudal vein was traced 

 only to its point of bifurcation in the basal canal of the caudal 

 fin. No caudal ray veins were seen emptying into these short 

 caudal fin veins, but as both caudal ray arteries and lymphatics 

 were clearly defined, the absence of such vessels could hardly be 

 attributed to faulty technique; tience the caudal ray lymphatic 

 vessels and the caudal fin lymphatic trunks in Clinocottus may 

 function as both lymphatics and veins. All of the microscopic 

 preparations clearly demonstrate that the red corpuscles greatly 

 outnumber the white in all the longitudinal lymphatic trunks. 



This study to a considerable extent supports the hypothesis 

 set forth in 1907 (p. 93) and in 1908 (pp. 72-3) and also prev^iously 

 championed by Favaro that the lymphatics of fishes have evolved 

 from veins, the evidence of course being derived solely from a study 

 of comparative anatomy. In the Selachians these trunks have 

 every indication of being veins for there are numerous connections 

 with the veins throughout the entire body; while with the Tel- 

 eosts these trunks are undoubtedly lymphatics. The Ganoids 

 appear to be a sort of intermediary; Polyodon, a cartilaginous 

 Ganoid, leaning toward the Selachians ; while Lepisosteus, a bony 

 Ganoid, inclines toward the Teleosts. It was shown in these 

 Ganoids that connections with the venous system are quite nunier- 



