BLOOD-VASCULAR SYSTEM OF THE LORICATI 75 



and the second and third neural arteries (fig. 5 ; Neu.A.2„„j3) 

 supply the dorsal branchial retractor muscles and the anterior 

 forks of the kidney in addition to the musculature already 

 described. 



HcBmal Arteries (fig. i ; Hae.A.).— These vessels arise from 

 the ventral side of the caudal artery, a little behind the corre- 

 sponding neural arteries, and crossing over the caudal vein run 

 ventrad between the haemal spines and the haemal lymphatic 

 vessels. Near the end of the spines they give off the ventral 

 lateral arteries (fig. i ; V.Lat.A.) for the great lateral muscle, 

 then curving cephalad, break up among the superficial and 

 profundus anal ray muscles in like manner to the neural arteries 

 in the dorsal fin musculature. The homologous intercostal 

 arteries of the visceral body wall have their origin in a common 

 vessel, which supplies also the kidney and often the reproduc- 

 tive organs. 



{b) Renal and Spermatic Arteries. — As has just been stated, 

 the renal and spermatic arteries as well as the intercostals often 

 have their source in one and the same artery, which is prob- 

 ably homologous with the haemal arteries of the caudal region. 

 For convenience we will speak of these common trunks in the 

 region of the anterior part of the kidney as the intercostal ar- 

 teries and in the region of the posterior part of the kidney, 

 where the main branch goes to the reproductive organs, as the 

 spermatic arteries. 



Intercostal Arteries (fig. i ; Intc.A.). — These vessels arise 

 from the ventral side of the aorta, in the region of each alternate 

 vertebra, and passing across the lateral surface of either side 

 of the kidney, they give off several renal arteries (fig. i ; Ren. 

 A.) for the kidney ; but the main trunks or intercostal arteries 

 proper continue ventrad between 2 myotomes and anastomose 

 with branches from the ventral artery, the so-called ventral in- 

 tercostal arteries. 



Spermatic Arteries (PI. I, figs, i and 10; Sper.A.).— In 

 both male and female there are at least 3 spermatic arteries, 

 which always cross the left side of the kidney, giving off 

 several renal arteries and one intercostal artery before leaving 

 the kidney for the reproductive organs. These arteries increase 



