28 Cincinnati Society of Natural History. 
much variation in this respect, however. Sometimes a 
somatic and one renal vessel arise together, and sometimes 
the renal vessels arise independently. 
(g) The genital branches (Figs. VII, XVIII, XX, gen) 
arise from all the mesenteric arteries in the region of the 
testis in the male, and the ovary in the female. Occasionally 
branches arise independently from the dorsal aorta. The 
genital branches pass out in the genital ligament (a special 
fold on the right side of the mesentery). Soon after enter- 
ing this fold the genital vessels, for the most part, unite to 
form a longitudinal commissural vessel. (Fig. VII.) From 
this vessel a large number of smaller vessels run out toward 
the testis or ovary, branching and anastomosing freely. A 
capillary network is formed in the membrane surrounding 
each ovum, or lobule of the testis. 
Behind the cloaca, the aorta continues immediately below 
the notochord in the median line, but here, as might be ex- 
pected, only the somatic branches are givenoff. On reaching 
the median ventral plate, the aorta divides into a right and a 
left branch, each of which passes backward on the corre- 
sponding side of the plate. Lateral branches are given off 
to supply the muscles and integument of the caudal region. 
In the caudal fin, small vessels run out distally correspond- 
ing to each fin ray. 
GENERAL VENOUS SYSTEM. 
The veizs of the Bdellostoma may be included under two 
separate systems—the gevera/ system, and the porta/ system. 
The general venous system is larger, including all those 
veins through which the blood flows into the sinus venosus. 
(Figs) Ky x1, RVI XVM SS)» “Anteriorly i -where rit 
empties into the auricle, the sinus is narrow, and receives 
the inxferior jugular vein (jv). Posteriorly, behind the auricle, 
the sinus is dilated, and receives on the left, the /é/t 
anterior cardinal vein (acl.) anteriorily, and the common car- 
dinal vein (pec) posteriorly. On the right side enter the 
anterior and posterior hepatic veins (ha, hp). 
Beginning with the general venous system in the head 
region, we find the superficial anterior cardinal vein. (Figs. 
16 
