90 
ZOOLOGY OF THE FAR EAST. 
situated within the line of the ventral setal bundles and not far from its fellow of 
the opposite side. There are no penial setae. The spermathecal apertures are just 
behind the ventral setae of segment x. 
The dorsal setae begin in segment ii and consist of hairs and needles. The hairs 
are usually one per bundle, rarely two, and occasionally they may be absent from a 
bundle; they are comparatively short, — about 37 mm. long, or not more than about 
twice the length of the needles. The needles var}^ somewhat in length ; in segment v 
they were measured as being 2 mm., and further back 15 mm. The distal end 
terminates in a single point (fig. la); the nodulus is slightly distal to the middle of 
the shaft (in the anterior segments), or (further back) at the middle. The total 
number of setae per bundle is seven or eight in the most anterior segments, soon 
diminishing to six, five, four or even three. 
The ventral setae begin in segment ii and are absent from xi. They are needles 
with the usual double curve, five to nine per bundle in the anterior part of the bod}^ 
and three or four behind the genital region. In length they measure 18 mm., and 
the nodulus is very slightly distal to the middle of the shaft ; the tip is blunt and 
single as a rule, but may show two short stump-like points (fig. ib). 
Internal Anatomy. 
The alimentary canal is but httle differentiated after the pharynx. 
The dorsal vessel is ventral in position from its hinder end as far forwards as the 
clitellar region ; the dorsal and ventral vessels may be seen in transverse sections as 
a pair of canals one on each side of the ventral nerve cord. There is one pair of 
hearts in segment ix. 
As in Branchiura sowerhyi^ a striking feature of the ventral nerve cord is the size 
of the giant fibres. Of these there are two which in places reach a really enormous 
thickness, and in addition one or two others are seen of much smaller size. In the 
middle of the body the nerve cord has, in one section, a transverse diameter of '072 
mm., while the largest giant fibre measures 046 mm. in its longest diameter; in seg- 
ment xiii the cord is 123 mm. in transverse diameter, and the largest fibre "05 mm. 
The giant fibres are however of irregular thickness, and are especially contracted 
where the cord passes through the septa. 
The testes, in segment x, attached to septum 9/10 near the ventral body- wall, 
are large and tend to be folded round the spermathecae. The ciliated funnel is a 
large irregular folding of the anterior face of septum lo/ii. The anterior spermsac, 
in ix, is single, small, and situated dorsal to the alimentary canal; the posterior, also 
single, extends back as far as segment xvii. 
The male deferent apparatus is shown diagrammatically in fig. 3. The vas 
deferens begins as a wide tube, 40 in diameter at its commencement behind septum 
lo/ii; passing backwards on the inner side of the coelomic chamber, to be described 
later, it becomes surrounded by a cellular "prostatic " investment — a large mass of 
cells enveloping the vas deferens, atrium and par atrium ; curving upwards, and while 
surrounded by the prostate, the vas deferens joins the posterior wall of the atrium 
