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Transactions of the Royal Society of South Africa. 
which appears to vary considerably in development, because in some 
specimens it extends only along two-thirds of the parasite, whilst in 
others it can be seen to begin practically immediately after the swelling 
of the oesophageal bulb. It is usually straight or only slightly sinuous in 
its course. In the anterior portion its function is testicular ; about half- 
way it thickens, approaches the ventral wall, and maintains this position 
in acting as vas deferens (Fig. 1), but becomes thinner again in nearing 
the cloaca. 
The spicules are spear-shaped when seen from the ventral side ; their 
lateral margins show two bulbar swellings, one in the anterior third and 
the other about the middle. The edge is thickened in the anterior por- 
tion, which shows a triangular protuberance ending in a thin pedunculated 
process. 
The length of the spiculae varies between 142 fx and 159 fx. 
The principal muscles in relation with the copulating apparatus, which 
are most easily detected, consist in a pair of powerful retractor muscles 
(Figs. 1, 6, 7 sp.rt.), of which one end is inserted on the pronounced edge 
of the spicule and the other on the side-wall of the body, when extended 
they measure about 250 /x. In addition a pair of exertor muscles (Figs. 
1, 6, 7 sp.et.), which are somewhat shorter and broader, and inserted on 
the edge of the spicule and the inner side of the bursa. Connected with 
the copulatory apparatus are three pairs of muscles whose precise function 
is still unclear (Figs. 5, 6, 7 d.m.). 
On both sides oblique muscles are noticeable, which converge towards 
the middle ventral line. They are so thick that in several portions it is 
not possible to distinguish separate bundles. They begin a little way 
above the bursa, and on being measured in a straight line are found to 
extend about 280 ^. These are commonly called bursal muscles, but 
would be more appropriately named incurvating muscles of the posterior 
extremity (Figs. 1, 6, 7 b.m.). 
The nomenclature adopted in relation to the ribs of the bursa is that 
suggested by Looss (1905). 
The single costa dorsalis (Figs. 6, 7 c.d.) divides half-way in two 
branches ; in some instances no further bifurcation is noticeable, but in 
others more or less distinct ramification takes place, as in Fig. 8. 
On each side there is a costa dorsalis externa (Figs. 6, 7 c.d.e.), some- 
what shorter, thinner, and more tapering than the dorsal rib. 
In front of the costa dorsalis externa a stout root divides in three 
broad ribs; the costa lateralis posterior (Figs. 6, 7 c.l.p.), which is some- 
what thinner than the following two ; the costa lateralis media (Figs. 6, 
7 c.l.m.) and costa lateralis externa (Figs. 6, 7 c.l.e.). 
The next in order are two costae ventralis (Figs. 6, 7 c.v.), the inner 
one being somewhat thinner than the other. 
