166
Studies on the Family Heterophyidae Odhner, 1914
Prominent, deeply staining and fair-sized gland cells are present in the pre-
acetabular part of body. The subterminal, muscular oral sucker measures
0.48—0.62 × 0.42—0.56 in size. The acetabulum is feebly muscular and
spherical, measuring 0.84 —1.18 in diameter. It lies embedded in the ventral
surface of the huge ventro-genital sinus situated just behind the first quarter
of body length. The latter is a spacious pouch on the ventral body surface
enclosing the poorly muscular acetabulum, a well-developed gonotyl and the
genital pore. The genital pore lies in the ventro-genital sinus just in
front of the acetabulum. The acetabulum as well as the gonotyl are highly
mobile and variable in position. The ventro-genital sinus opens to the ex-
terior through a small, triangular opening on the ventral surface, a little behind
the intestinal bifurcation. Sometimes the chitinous and roughly triangular
gonotyl is projected out of the sinus. Well developed retractor muscles are
present in connection with the gonotyl and the acetabulum. The pre-
pharynx and the oesophagus are very small and are visible only in the fully
extended worm. The pharynx is well developed and measures 0.36—0.48
× 0.42—0.54 in size. The broad straight caeca end blindly a little in front
of the hinder end of the body.
The excretory pore is situated terminally at the posterior end and is guard-
ed by a prominent sphincter. The bladder is Y-shaped, with its cornua ex-
tending anteriorly up to the level of the pharynx.
The testes are composed of a large number, thirty-five to fifty distinct,
small, spherical or oval follicles situated in the posterior third of body,
mostly in the intercaecal space, often overlapping one another and the
caeca on the sides. The testicular follicles measure 0.16—0.3×0.12—0. 24
in size and do not extend posteriorly beyond the blind ends of the
caeca. The vesicula seminalis is moderately long and sinuous, measuring
0.7—0.95 in length, with a few constrictions and extends posteriorly
to a short distance behind the first half of body. Anteriorly it opens
through a small, plug-like structure into a 0.42—0.7 long pars prostatiea
which is surrounded by poorly developed prostate gland cells. The
pars prostatiea is attenuated anteriorly and slightly swollen posteriorly
and extends a little beyond the hinder margin of the ventro-genital sinus. The
narrow ductus ejaculatorius is of about the same length as the pars prostatica
and joins the terminal part of the feebly muscular metraterm. The retractor
muscles, pars prostatica, ductus ejaculatorius and the metraterm all lie along
the right side of the ventro-genital sinus.
The ovary is situated in the median line just in front of the testicular mass.
It is usually a compact, roughly triangular or oval structure of 0.43—0.54
× 0.3—0.4 in size. Rarely it is slightly lobed and of irregular shape. A thin-
walled receptaculum seminis, 0.44—0.68 × 0.34—0.5 in size, lies obliquely
behind the ovary on the left side. A small Laurer's canal is given off from the
neck of the receptaculum seminis. The Mehlis gland lies between the recepta-
culum seminis and the ovary, partly overlapping the latter. The vitellaria
are lateral, extending from a little behind the level of the posterior margin of
the ventro-genital sinus to the hinder end. The vitellarium of each side is