VASCULAR SYSTEM OF PHERE'TIMA O77 
laries which run longitudinally parallel to one another. These 
branches of the dorsal vessel have a series of paired valves 
along their length between the point of their origin and the 
place where there is the bulb-like dilatation. The bulb-like 
dilatation which occurs at the distal end of all the ‘ hearts ’ 
contains a pair of thick valves pointing away from the dorsal 
and towards the ventral vessel, as shown im fig. 11. 
The blood to the gizzard, therefore, is supplied from the dorsal 
vessel by the pair of branches in this segment ; while the eapil- 
laries of the supra-intestinal vessel, which has its beginnings 
here, collect blood from the gizzard and take it into that 
vessel. 
Seventh Segment.—In the seventh segment there is 
a pair of ‘lateral’ hearts, each of which is joined below both 
with the ventral and the lateral oesophageal vessels, which 
latter are themselves joined together by a cross channel. 
In its upper part each of this pair of ‘ hearts’ is thick-walled 
and has valves leading blood outwards, but in its ventral part 
each ‘heart’ is thin-walled and has also no valves in it. 
There is no doubt that the blood flows from the dorsal to the 
ventral vessel ; but it seems probable that the supply of blood 
in the ventral vessel, which is very thin in this region and 
contains little blood, is also replenished from the lateral 
oesophageals, which are always large and full. 
Sixth, Fifth, and Fourth Segments.—In the 
sixth segment, and algo in the fifth and fourth, there is a pair 
of branches given off from the dorsal vessel each of which 
has a pair of valves leading outwards near its origin, and 
supplies blood to the masses of pharyngeal nephridia in each of 
these three segments. These branches are also pulsatile and 
can therefore be named ‘ hearts ’. 
Third Segment.—In the third segment before the dorsal 
vessel breaks up anteriorly, it gives off a pair of branches 
to the pharyngeal mass behind the cerebral ganglion. These 
branches also possess valves near their origin which direct 
the flow of blood outwards. 
