ELEDONE. 329 
The afferent vessel of the gill runs along the dorsal 
wall of the branchial cone (Pl. VIII, fig. 63), ventral to 
the spleen, giving off alternate branches on its way, to the 
alternating internal and external gill leaflets. Narrowing 
down with the gill, it runs to its tip. The branch to the 
leaflet runs in the supporting pillar, and, therefore, on 
the side next to the gill cavity. Running along to the 
ventral side of this cavity, it joins another venous vessel, 
parallel to the main afferent vessel, and forming the 
ventral wall of the gill cone (fig. 63). Again, each of 
these vessels to the leaflets or primary elements of the 
gill, gives off similarly alternating vessels to the 
secondary elements of the gill (fig. 63, V,, V,,), and so 
on. However, these vessels run along the outer edge of 
the secondary, tertiary, &c., elements (fig. 62). On the 
internal surface of the gill, where the leaflets do not 
bear secondary elements all along their axis, the four 
lowest folds receive blood from a common vessel (fig. 63). 
The secondary vessels running up along the outer edge 
of the corresponding folds, decrease in size and end on 
the external surface of the gill, at the tip of the fold 
(fig. 62). As there are eight series of gill elements, and 
consequently eight series of vessels, the ultimate ones 
are extremely fine. They open into a venous lacuna in 
the gill filaments, and the blood which by now is in 
ereat part aerated and arterial, is gathered up again into 
a network of arterial capillaries. Each accessory leaflet 
receives blood from a vessel given off by the vein parallel 
to the main afferent vessel, and described above. This 
vessel runs along the outer surface of the accessory leaflet 
and divides up exactly as do the branches to the secondary 
elements of the gill (fig. 63). 
The finest arterial capillaries of the efferent vessels 
are situated in the eighth elements of the gill. Hach 
