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more caudal in the animal than shown in the figure. However, it has proved impossible
to state exactly the most posterior limit. Each of the spicules is surrounded by a sheath,
the surf ace of which seems to consist of a chitin-membrane; on examination with immersion
(apochr. 2 mm.) it presents a most peculiar spotted surf ace, each spot being due to a dimi-
nutive circle and most Hkely representing holes or grooves. Somewhat more caudally
situated, not far from the distal end of the thicker spicula, another piece of sheath is
found, the object of which possibly might be to make the two spicules keep their
distance and to support the whole sheath-apparatus. The latter piece seems bigger
and more thick-walled than the sheaths which compass each spicule. A faet which
renders it difficult to accomplish an examination of this part of the worm, is the
highly developed muscular system which is found here.
From the neighbourhood of the anus, broad muscular bands arise, running
partly ventrodorsally on each side of Rectum and Ductus ejaculatorius, partly obliquely
forwards, partly obliquely backwards or flabelliform towards both sides.
The interior genital organs are found corresponding to the usual type. The testis
being single presents quite a straight line with no curvings, and almost reaches as far as to
the proximal end of the oesophagus, where it turns, running back in caudal direction,
parallel to itself, and terminating in a small retort-shaped dilatation. The returning
branch is always quite short (PI. IV fig. 29). In exceptional cases the course may be
somewhat different, f. instance when after returning the testis turns once more, and
for a little while takes a cephalic direction, after which it terminates in the usual
way, bent caudal. In no specimen was the testis found surpassing the limit between
the oesophagus and the intestine. Usually the point of turning will be at a distance
of c. ^2 mm. from the said limit. The testis does not vary in width, the minimal
diameter being near to the turning where it measures 24«. In the middle of its
length it is about 60 fi and its maximal width is found to be 72 p.. The hind part
of the genital duet presents a differentiation; posterior to testis it narrows to a
narrow duet, which evidently serves as nothing but a conduct-pipe, and there-
fore may be pointed out as Vas deferens. It is c. 70 // in length, although no
exact measure can be given as seen from flg. 27 PI. IV; the distal end of the testis
is tapering evenly into a conical part, which passes into the vas deferens without any
distinct line of demarcation. The vas deferens then again increases evenly in width
and passes into a dilated part reaching towards the anus, nearly in front of which
it narrows into a short Ductus ejaculatorius. The dilated part which is to be
marked out as vesicula seminalis has a length of a little more than one mm. and
often is brimful of spermatozoa. When placing the worm alive under the cover-slip
the spermatozoa often by the pressure may be forced out through the anogenital opening.
They then appear as small regular globular-cells.
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