BLOOD-VASCULAR SYSTEM OF THE LORICATI 75 
and the second and third neural arteries (fig. 5; Neu.A.,,.3;) 
supply the dorsal branchial retractor muscles and the anterior 
forks of the kidney in addition to the musculature already 
described. 
Hemal Arteries (fig. 1; Hee.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 hemal spines and the hemal tymphatic 
vessels. Near the end of the spines they give off the ventral 
lateral artertes (fig. 1; 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. 
(6) Penal and Spermatic Artertes. — 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 hemal 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. 1; 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 arterzes (igon ; Ken: 
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 Arterzes (Pl. I, figs. 1 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 
