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Tapeworms of Birds 
continuous layer of transverse and dorso-ventral muscles: between each 
proglottis and its neighbour therefore is a small thin parenchymatous 
space, bounded anteriorly and posteriorly by these muscle layers. 
These plates in the anterior portion of the strobilus are more or less 
interrupted by the strands of the longitudinal muscles, and in themselves 
are defective, having numerous large spaces between their constituent 
muscles. More posteriorly these defects disappear and the longitudinal 
muscles lose their continuity. In the segments ready to be detached, 
the process reaches its conclusion. The plates are formed by an uninter¬ 
rupted muscle layer in which the distinction between transverse and 
dorso-ventral muscles has nearly disappeared, the parenchyma in the 
enclosed space degenerating. When the proglottis is detached these 
plates contract, drawing its edges together. 
Excretory System,. The excretory system in this form is so minute 
that little of its general plan could be ascertained. There are the usual 
four longitudinal excretory vessels, the ventral of which soon disappear, 
and their transverse commissures. Round the anterior part of the 
rostellum is a circular commissure into which the longitudinal excretory 
vessels open, and just posterior to it is a second, connecting the four 
vessels. Numerous fine branches radiate from this and the longitudinal 
vessels, some of them apparently leading to the suckers although this 
could not be definitely ascertained. There is evidence of an elaborate 
and definite system in the scolex, but owing to gaps in the vessels and 
to their exceptionally small size, it was found impossible to unravel it. 
Nervous System. In the body, the nervous system consists of the 
usual two main longitudinal nerve trunks and their numerous branches. 
The main longitudinal nerves pass unaltered through the neck. Just 
posterior to the suckers each divides into two, the two branches of each 
side merging after a short course into a central nerve mass or “brain.” 
This latter lies in the centre of the proglottis just posterior to the hinder 
border of the suckers. It is a flattened irregular six-pointed mass with 
a small antero-posterior diameter, the longitudinal nerves entering it 
some little distance from its lateral extremities. Of the six points, the 
two dorsal and the two ventral give rise to nerves leading straight to 
the posterior borders of their respective suckers. The nerves from the 
two lateral points run anteriorly as far as the anterior border of the 
suckers and there join a circular commissure. The commissure touches 
the inner borders of the suckers and supplies them with numerous 
nerves: in the spaces between the suckers it bends to the exterior, and 
half-way between them expands into a small ganglion from which nerves 
