LYMPHATICS IN TAIL REGION, SCORP^NICHTHYS 13 



point, however, was not determined for a certainty. At the apex of 

 the neural spine a dorsal lateral artery (figs. 4a, D.L.A.) is sent off 

 lateral along the intermuscular septum to the periphery, supply- 

 ing the dorsal portion of the two adjacent myotomes. At this 

 point the neural artery makes a cephalic bend to cross the bases 

 of the depressor and levator muscles of the adjacent dorsal ray. 

 After which it takes another turn to pass dorsad between this 

 levator muscle and the next depressor muscle to the level of ex- 

 trinsic muscles of the dorsal fin; where it divides into an anterior 

 and a posterior branch. The main stem and these branches sup- 

 ply the intrinsic and extrinsic muscles mentioned above, and also 

 send off two dorsal ray arteries (fig. 4a, D.R.A.), which follow 

 up the posterior side of their respective rays, supplying each and 

 their fin membrane. 



The ventral branches of the caudal artery or the haemal arter- 

 ies (figs. 4, 4a, 9 and 10, Hce. A.) after leaving the haemal canal 

 pursue a similar course ventrad to that of the neural arteries dor- 

 sad. At the apex of each haemal spine a ventral lateral artery 

 (figs. 4, 4a, V.L.A.) is given off to the periphery. It passes 

 along the intermuscular septum, between two myotomes, supply- 

 ing each. The main stem of the haemal artery crosses a depres- 

 sor and a levator muscle of the adjacent anal ray, and then con- 

 tinues ventrad to the extrinsic muscles of the anal fin between the 

 above levator muscle and the next depressor muscle. Like the 

 corresponding neural trunks upon reaching the extrinsic muscles 

 it separates into an anterior and a posterior branch, which sup- 

 plies the extrinsic muscles and the levator and two depressor 

 muscles, and sends off two anal ray arteries (figs. 4a, A.R.A.) to 

 the posterior surfaces of two rays, supplying them and thefr fin 

 membrane. 



Interseg^nental or intercostal veins. (Figs. 4 and 4:a,Neu. and Hce. 

 V. fig. 9, Neu. and L.V.; L.V., and Hce. V.). — The arrangement 

 and distribution of these veins is identically the same as the cor- 

 responding arteries, with this difference that they lie in the inter- 

 mediate alternate intermuscular septa and terminate in the cau- 

 dal vein. So that the above description of the distribution of the 

 neural, haemal, lateral, dorsal or ventral lateral, and the dorsal 



