580 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
fold here sends off rather larger vessels, that form a some- 
what coarser meshwork in the seventh element, and so 
on, till the secondary elements are reached. Now, in 
the axis of each gill filament, about halfway between 
the internal and external surfaces, runs the artery from 
this leaflet, out to the efferent gill vessel (fig. 61, A,). 
It originates in branches from the network of vessels in 
the secondary elements of the gill, and the latter must 
be turned aside to disclose both the artery and the 
network (fig. 61, WV.). 
The efferent vessels of the accessory leaflets also 
originate in a network of capillaries. The meshwork 
of arteries increases in size in succeeding elements of the 
gill. Ultimately they open into two vessels:—(a) A 
sinuous vessel common to, and between the two leaflets, 
and opening into the efferent vessel of the true leaflet 
between them, but on the opposite side of the gill (fig. 65, 
and (6) A sinuous vessel on the other side of each 
accessory leaflet, running into the efferent vessel of the 
leaflet adjacent (fig. 63, 2). 
The so-called Spleen or branchial gland of the 
Cephalopods, would appear to have some intimate con- 
nection with the blood, as it is irrigated by both arterial 
and venous blood, and is placed close to the gill. It is 
built up of polygonal cells, separated by lacunae of 
yarious sizes containing blood (Pl. VI, fig. 63a; 6.s. and 
l.b.s.). There are no true capillary vessels whatsoever. 
It receives blood: (1) from branches which, coming 
from the afferent vessel, furnish venous blood (fig. 
63, Affv); and (2) from arteries running down 
the supporting pillars of the branchial leaflets. These. 
arteries originate in a network formed by the arteries 
of the accessory gills (fig. 63). This blood mixes 
in the intercellular lacunae of the branchial gland, 
ss 
