78 
from the 2nd to the 14th vertebra. Its greater portion is 
covered laterally by the transverse processes and ribs of 
those vertebra. (Its ventral surface forms the roof of the 
body cavity. Posteriorly it increases very much in thick- 
ness dorso-ventrally and oceupies the angle formed by the 
vertebral column and the nearly perpendicular 1st haemal 
spine and axonost, and laterally by the 7th to 10th ribs. 
It is for the greater portion of its length a single un- 
divided mass, but anteriorly is produced into two tapering 
and diverging horns—the head portions of the kidney, 
which he laterally and dorsally from the esophagus. The 
right unpaired cardinal vein runs along the middle line as 
far as the thickened portion, and is visible on its ventral 
surface. Dorsally the aorta lies in a groove in the middle 
line, and this with the cardinal vein separates the 
uriniferous tubular tissue into two paired masses. Only 
in the thickened posterior portion of the kidney is this 
tubular tissue continuous across its whole breadth. 
At the dorsal posterior corner of the kidney the caudal 
vein enters as a single vessel which almost immediately 
divides into paired portions. Apparently it does not 
become continuous with the cardinal vein, but breaks up 
round the uriniferous tubules, though there are doubtless 
anastomoses between the two vessels. The extreme 
ventral portion of the kidney is produced downwards into 
paired tips, and into these the paired genital veins (V.gen. 
fig. 21) enter. Along the dorsal surface of the crgan other 
paired venous trunks (parietal veins) also enter. The 
most anterior of these vessels is shewn in fig. 22 entering 
the extreme anterior tip of the head portion of the kidney. 
The caudal, genital and parietal veins, with the renal 
arteries are the afferent vessels of the kidney. The paired 
posterior cardinal veins are its efferent vessels. 
The Ureter (U/ret. fig. 21) leaves the ventral and pos- 
qe 
