220
Morphology of a New Genus of Amphistomes
For the study of the lymphatic system it was
found desirable to keep the specimens in corrosive
sublimate for a lesser time, usually six hours. After
washing in the usual way they were placed in ½ per
cent solution of sodium thiosulphate (hypo) which
was allowed to react on the specimens for ½ to 1
hour. The material was then thoroughly washed
in water and cleared in glycerine. The lymph
vessels took a beautiful yellow tinge and could be
clearly traced through the specimens.
Acetic alum carmine and Ehrlich's acid hæma-
toxylin gave good results for the whole mounts and
sections.
Olveria indica N.G., N.SP.
The worms are flat and slightly elongated,
measuring 6.14-7.07 mm. in length and 2.35-3.35 mm.
in greatest breadth. They are widest in the middle
and gradually taper towards the anterior end. The
posterior end is, however, rounded. There are
cuticular papillæ present in the region of the mouth
and the genital sucker. The cuticle is inturned
both at the mouth and the genital opening and
shows cuticular papillæ in these regions. It is
produced into small ridges (denticles) at the mouth
and is continued into the entire length of the muscular
portion of the œsophagus forming its inner lining.
The mouth opening is anterior and terminal and is
surrounded by an oral sucker. Arising from the
postero-lateral sides of the oral sucker are two
pouches, one on each side, which are fused with it.
The acetabulum at the posterior end of the body
is well developed and larger than the oral sucker. It
is oval in shape and measures 1.3 mm. by 0.73 mm.
in size.
The mouth leads into an elongated recurved J-
shaped œsophagus which consists of two portions—
an anterior long muscular portion which forms the
elongated bar and the curve of the letter ' J ' and
a posterior non-muscular portion which connects the
former with the intestinal bifurcation. The non-
muscular portion of the œsophagus is surrounded
by a large number of unicellular gland cells. The
whole of the œsophagus measures 3.6 mm. in length.
The cæcal bifurcation is about 1.74 mm. from the
anterior end of the body. The cæca are long, coiled
slender tubes, making two to three antero-posterior
loops in their course, and, terminating blindly near
the ovary, in front of the posterior sucker.
The excretory pore is situated dorsally at the
posterior end of the body immediately in front of
the posterior sucker and a little behind the opening of
the Laurer's canal. The excretory bladder is fairly
large and more or less rounded in shape. It is
placed dorsally slightly overlapping the posterior
sucker. The two longitudinal excretory ducts
arise from the bladder, one on each side and, run
forward towards the anterior end, terminating at
the level of the oral pouches. During its course
about the middle of the body, each longitudinal
duct gives out internally one branch which runs
towards the median line and meets the fellow of the
other side at about the level of the bend of the J.
shaped œsophagus- and thus gives an H-shaped
appearance to the excretory system which is essen-
tially a Paramphistomum pattern. A small branch
from the point of junction of the two transverse
ducts runs anteriorly to the œsophagus. Other
small branches are also given off from the longitudinal
ducts and they are mainly distributed over the
intestinal cæcum, of each side and thus form a com-
plete network of excretory tubules round them.
It may be pointed out here that it is the first record
of a network of excretory tubules surrounding the
intestinal cæca in the Amphistomes and is represented
in the accompanying microphotograph (Plate XII,
fig. 3). Still smaller branches and their sub-branches
run to every part of the body and the tubules
anastomose with each other.
The lymphatic system consists of two longitudinal
vessels, one on each side of the body, running slightly
internal to the intestinal cæca. They send out
branches in all directions, dorsally, ventrally, laterally
and mesially. The main longitudinal vessels as
studied in the whole mounts and confirmed by a
study of the serial sections are as follows : At the
posterior end of the body each longitudinal vessel
breaks up into three branches which divide and
extend into the tissues of the posterior sucker,
Immediately in front of the sucker they form a
lymphatic plexus on each side. Two branches are
supplied to the excretory bladder from each side,
which get distributed round the bladder in small
ampulla-like vessels. Anteriorly each longitudinal
vessel gives out one branch to the testis of its side
and a few to the intestinal cæca. The ovary gets
its supply from one of the branches supplying the
testis. More anteriorly each longitudinal duct gives
out one branch internally which divides and supplies
the genital sucker and the œsophagus, and, further
forwards divides and sub-divides in the substance of
the oral pouch and. oral sucker. Just before reaching
the oral sucker the longitudinal ducts form another
but smaller plexus on each side. The lateral branches
and their sub-branches have been observed to fuse
with each other and thus form a close network of
lymph tubules all over the body.
Female reproductive organs. The ovary is rounded
in shape, measuring 0.4-0.43 mm. in diameter,
and is situated at a distance of 1.1-1.13 mm. from
the posterior end of the body, slightly to the left of
the median line near the termination of the cæcum
of the side. The oviduct arises from the middle of
the mesial side of the ovary. Immediately after-
wards it receives the common vitelline duct and the
Laurer's canal and forms the öotype. The point of