ELEDONE. Fare 
towards the tip, from the base of the gill, the leaflets at 
first increase in size, the third pair being the largest, and 
from here they gradually decrease towards the tip. The 
aerating filaments stretch from the afferent to the efferent 
vessels, and each leaflet is separated from its neighbours 
by a sht. Hence water can pass in and out of the cavity 
of the gill either by the hole at the base, or by the slits 
between the gill leaflets. Looking through these slits on 
the external side of the gill, the leaflet of the other side 
may be seen (fig. 60, Z. and Z,). This sketch shows a 
part of the gill from the internal side. At the bottom is 
the branchial gland, and from it three gill leaflets may be 
seen running ventrally to the efferent axis of the gill. 
The centre leaflet has been taken away except for a part 
at the base, in order to show more clearly the two 
alternating ones on the opposite side. Posteriorly, these 
leaflets are attached to the outer side of the afferent vessel 
which runs up the gill on the inner side of the spleen 
(Pl. VIII, fig. 63), lessening in size as the gill narrows 
to the tip. Thus the afferent vessel, covered over by the 
general lining of the mantle cavity, forms the dorsal wall 
of the cavity of the gill. Similarly on the outer edge of 
the gill, the efferent vessel runs from its tip downwards, 
but a thin sheet of connective tissue (fig. 60, C.T7.), 
running inwards into the gill cavity from the efferent 
axis, along the median plane, separates the efferent vessel 
from the cavity of the gill, and forms the ventral 
boundary of the latter (figs. 60 and 63). 
The complex gill-leaflets are attached ventrally to 
this sheet of tissue. First considering each leaflet as a 
single sheet, it is seen that the aerating portion or 
filament is on the external side of the attaching pillar, 
and is consequently bathed in the water of the mantle 
cavity. Hence blood brought into these filaments for 
