444 MR. C. H. O'DONOGHUE ON THE 
middle line. Each cardinal sinus runs forwards as a fairly 
narrow vessel to a point just in front of the anterior mesenteric 
artery and then commences to widen out. At the anterior end 
the two sinuses occupy the whole of the region dorsal to the 
cesophagus right up to the pericardio-peritoneal septum and 
outwards to the sides of the body. The condition of the septum 
between the sinuses at the front end varies greatly in different 
specimens. It may be practically absent, represented only by a 
few strands, it may be well developed with perforations, or most 
frequently it is in a condition between these two extremes. ‘The 
posterior cardinal receives the renal veins, the genital sinus, the 
anterior parietal veins, the anterior oviducal sinus in the female, 
the sub-scapular sinus, the veins from the spinal cord, and at its 
front end the anterior cardinal sinus and the ductus Cuvieri open 
into it *. 
The Renal Veins (Parker) are represented by a series of efferent 
vessels leaving the kidneys. They do not appear as separate 
vessels outside that organ, as the wall of the posterior cardinal 
sinus is in contact with the mesial border of the kidney. 
2. The Genital Sinuses differ in the two sexes and will be 
dealt with separately. 
A. The Ovarian Sinus is a large trunk composed of numerous 
irregular factors and runs in the mesovarium dorsal to the ovary 
from its posterior end. A very similar but smaller vein is 
formed at the anterior end of the ovary, aud the two unite in the 
first third of that body and pass dorsally into the posterior 
cardinal sinus in the region where the anterior mesenteric and . 
henogastric arteries are given off from the dorsal aorta. Just 
before entering the posterior cardinal sinus it swells out some- 
what and receives the intestino-mesenteric vein. 
B. The Spermatic Vein (Parker) [Pl. I., R.S.] is subject toa 
considerable amount of variation, and often each testis possesses 
two separate veins. The posterior drains the hinder two-thirds 
of the testis and, passing dorsally through the mesorchium, joins 
its fellow of the opposite side to form a common genital sinus 
which opens into the posterior cardinal sinus. The intestino- 
mesenteric vein often joins the right spermatic vein just before 
it unites with the left. The anterior spermatic vein drains the 
front portion of the testis, in front of which it joins with its 
fellow and opens into the posterior cardinal sinus. Sometimes, 
perhaps more generally, this anterior spermatic vein is simply 
a factor of the posterior one, which is always the main vein. 
* It is stated that developmentally the anterior and posterior cardinal veins open 
separately on the anterior and posterior sides of the ductus Cuvieri respectively. 
That this description. given by Hoffmann (5), Hochstetter (8), Balfour (1), and 
others, is the correct one can easily be verified by reference to a series of sections 
of an embryo of S. canicula. In the adult, however, the actual anatomical 
relations are different, possibly because of the dilatation of the veins to form 
sinuses, and we find that the anterior cardinal sinus opens into the posterior cardinal , 
sinus by an aperture guarded by a valve, and the ductus Cuvieri projects as a short 
tube into the posterior cardinal sinus, opening therein by an oval aperture. 
