F. J. Meggitt 
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also communicate with each other once or twice. Apart from the 
commissures in each proglottis, the vessels on opposite sides communicate 
with one another in the scolex by two ring commissures, one nearly at 
the posterior hniit of the rostellum (p.r.c.) just where the lateral vessels 
join the main longitudinal one, and one at the extreme apex of the 
rostellum {a.r.c.). At the point where each main longitudinal vessel 
bends round to form the lateral vessel, a narrow branch {x) is given off 
anteriorly. This runs in a straight line, continuing the course of the 
longitudinal vessel, to the extreme apex of the rostellum : there it opens 
into the circular commissure (a.r.c.) running exactly under the cuticle 
and joining the four branches. In addition to this main plan there are 
numerous fine branches which run to the suckers and rostellum and 
anastomose with one another to such an extent that, owing to their 
small size, it is impossible to trace their course with any degree of 
certainty. 
Nervous System. 
The nervous system of this species (PI. XXI, fig. 11) has been entirely 
neglected by previous investigators. It consists essentially of two 
longitudinal nerve trunks (l.n.) joined in the scolex by two commissures, 
one dorsal and one ventral. Each nerve trunk extends from the posterior 
margin of the strobilus to a little below the centre of the suckers : it 
runs as usual in the parenchyma, externally to the excretory system, 
but internally to the musculature. At about the level of the posterior 
third of the suckers, the nerve is joined to its fellow of the other side by 
two commissures. These commissures do not form a nerve ring proper, 
but run postero-laterally round the rostellum so that their dorsal and 
ventral surfaces are considerably posterior to their junction with the nerve 
trunks. Each commissure is much swollen on the ventral and dorsal 
surface of the rostellum to form a small crescent-shaped “ brain ” (b) : 
the two junctions with the nerve trunks are also much swollen to form 
two lateral ganglia (l.g.) surrounded with dense masses of deeply staining 
cells. The whole circum-rostellar ring thus encircles the posterior third 
of the rostellum. On each side of the lateral ganglion, a small nerve is 
given off : tins runs outwards and slightly anteriorly to the centre of 
the corresponding sucker (s.n.) ; each sucker being supplied by one of 
the four nerves from the circum-rostellar ring. Slightly dorsal and 
ventral to the sucker nerves two other nerves are given off (r.n.), one 
on each side of each of the lateral ganglion as before. These nerves 
run anteriorly nearly to the apex of the rostellum where each branches 
