ELEDONE. 521 
the great vena cava; and the blood in the vena cava thus 
penetrates into this intricate system in the appendages on 
its way to the gill. Now externally these appendages are 
covered by the glandular wall of the kidney, as_ they 
encroach on the cavity of the kidney sac. They show 
many furrows and minute holes on their external surface, 
which are lined by the glandular kidney epithelium. 
Hence the blood contained in the vascular network in the 
appendages comes into intimate connection with the 
olandular cells of the kidney, and is deprived of its 
excretory products. ‘The appendages are spongy and 
yellowish in colour, and show through the ventral 
transparent wall of the fresh kidney. The two vessels 
running to the venae cavae from the venous sinus each 
oive off a small branch to the ventricle near their ventral 
ends (fig. 53, Cor.V.). Into the right abdominal vein 
opens a large vein formed by the union of many branches 
from the genital gland. Half way along its course this 
vein receives two lesser vessels from the dorsal region of 
the visceral envelope, and a branch from the spiral section 
of the sinus (fig. 53, V.H.V.). 
The Branchial hearts are purplish glandular organs 
at the base of each gill, into which the lateral venae 
cavae open, one at each side (Pl. VII, figs. 52 and 55). This 
round opening is guarded by two semi-lunar valves which 
open into the afferent vessel, and prevent the reflux of 
blood from the gill (Pl. VII, fig. 56). The branchial 
heart is an organ with very thick spongy walls, composed 
of soft cellular tissue. The central lumen, however, 
which these walls enclose is very small. On the internal 
surface of the wall numerous large and small holes may 
be seen, which lead into short canals (Pl. VII, fig. 56), 
from which other smaller passages lead off, and a third 
_ series from the second, and so on, the ultimate apertures 
