June, 1955]
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tubule enters the tail-stem and finally divides into two capillaries which end in
flame cells in the proximal part of the tail. Thus, there are altogether 20 flame cells ;
eight pairs in the body (each anterior and posterior collecting tubule receiving two
sets) and two pairs in the proximal part of the tail-stem. Such an arrangement can
be represented by the following formula :
2[(2 + 2) + (2 + 2) + 2] = 20
A distinct median caudal tubule passes from the excretory vesicle down the tail-
stem and divides at the bifurcation of the tail, each tributary so formed opening on
the inner margin of the furcal ramus about half its length. The ' Island of Cort'
is absent in this cercaria.
The genital system is represented by a cluster of small cells occupying a position
in the median line anterior to the bladder.
The cercariae develop in white elongate sporocysts in the digestive gland of the
molluscan host. The parthenitae are so slender that they entangle themselves to
appear like a mass of cotton wool. Entire sporocyst measuring up to 6.3 mm. in
length has been obtained. The organism bulges out at varying intervals throughout
its length and the lumen varies accordingly from 0.084 to 0.500 mm. The bulgings
are caused by the assemblage or crowding of a number of mature cercariae which
come out by bursting open the extended sporocyst wall. No birth-pore or excretory
structures could be seen in the sporocyst.
Cercaria mudaliari, sp. nov., closely resembles Cercaria douglasi Cort, 1917,
and the cercaria of Cotylurus flabelliformis [Faust, 1917] described by Olivier and
Cort [1941]. The latter two forms, while agreeing in many of the essential points with
those of the larva under study, differ from it in the following respects : The ' for-
ward projecting' spines found dorsal to the mouth opening are long and vary in
number from 16 to 20. The ventral sucker possesses several rows of spines which
are thin and elongate. Only one pair of bristles are found on the body, and the
flagellets (number not definite) on the tail-stem do not seem to be arranged in pairs.
Typical caudal glands are not present. Instead, only ' inconspicuous stellate cells
grouped along excretory tubule of tail-stem' are to be found. The eye-spots appear
as clear areas without pigment. The caeca and penetration glands have been des-
cribed as inconspicuous. The duct of the inner gland does not cross that of the
outer one. The excretory vesicle does not exhibit the appearance of a triglobular
structure. A small' Island of Cort' is present. In the cercaria of Cotylurus flabelli-
formis the tail-stem is longer than the body.
Cercaria sanjuanensis Miller [1927], while resembling the present one in possessing
a similar flame cell pattern, a pre-acetabular transverse commissure, tangle of main
vessels and four penetration glands anterior to ventral sucker, can be easily separated
from it in that in the former the eye-spots are lacking, no structures corresponding
to the caudal glands are present in the tail-stem, the caeca are made up of disjointed
parts, the penetration glands are coarsely granular and the transverse commissure
sends off short blind tubes anteriorly.
Among the Indian species, its nearest relative perhaps is Cercaria hurleyi Rao
[1933b] which can be distinguished from the new cercaria by the following features: