LYMPHATICS IN TAIL REGION, SCORP^NICHTHYS 11 



column, the myelon, all of the fins except the caudal, and the con- 

 nective tissue surrounding the vertebral column, the body muscles, 

 and the periphery. Ordinarily, as shown in fig. 9, below each ver- 

 tebra, two lateral branches and one ventral branch are given off 

 or received by the longitudinal blood vessels of the haemal canal. 

 One of the lateral branches is a vein and the other is an artery; 

 while half of the ventral branches are arteries and half are veins, 

 there being an artery for each alternate vertebra and a vein for 

 the intermediate alternate vertebrae. Upon examining fig. 9 

 from cephalad to caudad it will be seen that the arteries and veins 

 alternately shift from one side to the other. For example, under 

 vertebra numbered 14 the artery passes to the right side and the 

 vein to the left; while under vertebra numbered 13 the artery goes 

 to the left and the vein to the right. Furthermore, all of the ar- 

 teries which pass in a lateral direction, upon leaving the haemal 

 canal curve around to the side of the centra; where one-half of 

 them, the lateral arteries (fig. 9, L.A.), follow the intermuscular 

 septa laterad to the periphery, and the other half (fig. 9, Neu. and 

 L.A.) bifurcate; one branch, the lateral arteries (figs. 4 and 4a, 

 L.A.), follow the intermuscular septa laterad to the periphery, 

 and the other branch, the neural arteries (figs. 4 and 4a, Neu.A.) 

 pass dorsad along the neural spines to the periphery. The same 

 correlation occurs with the veins that pasg in a lateral direction ; 

 one-half of them (fig. 9, L.V.) to trace backward, simply pass 

 laterad to the periphery; while the other half, (fig. 9, Neu. and 

 L.V.) to trace backward, bifurcate, one branch (fig. 4a, L.V.) 

 going lateral to the periphery, and the other (fig 4a, Neu. V.) 

 dorsad to the periphery. The arrangement of the ventral 

 branches of the haemal trunks is less complicated. Below one 

 centrum an artery (figs. 9 and 4a, Hce.A.) passes ventrad along 

 its haemal spine to the periphery, and from under the next ver- 

 tebra to trace backward a vein (figs 9 and 4a, Hce. V.), passes 

 ventrad along the haemal spine to the periphery, and so on, the 

 veins alternating with the arteries. 



The outcome of this complex arrangement is, that each alter- 

 nate dorsal intermuscular septum receives a neural artery, and 

 from every intermedian dorsal intermuscular septa there comes 



