110
THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VII, II
Rao and Ayyar [1935] reported the case of a dog from Jubbulpore which evidently
had S. suis infection. Hence it may be that this parasite is more widely spread in
India than is known at present; nor is there any information regarding the patho-
logical conditions set up by this parasite in pigs and the consequent economic loss
to the pig-breeding industry in India.
Description of the ovum. It was possible to obtain ample material for study
of the ova. The blood-tinged flakes of mucous contained a very large number of
living, dead and ill-developed ova. The dimensions in microns are as follows :—
Length 90 to 125. Breadth 40 to 65. Length of spine 5 to 7.5. One side of the
ovum is slightly flattened, making it sub-oval in shape and the spine is subterminal,
making a wide angle with the flattened side (Plate XII, figs. 1 and 3). In some
ova, the spine is curved slightly away from the flattened side or base, though the
majority of them have their spines inclined towards it. The flattened side in
some of the well-developed ova showed a slight concavity so as to give the ovum a
shape somewhat like that of a bean.
Description of the miracidium. The miracidium inside the egg is apparently
enclosed in a vitelline membrane which becomes more evident when the ovum is
put in fresh water. The miracidia, while in the egg, show up the details of their
anatomy through the transparent egg-shell. Many of the miracidia, while still in
the egg, appear to possess what may be called ' shoulders ' on the antero-lateral
margins as depicted in Plate XII, fig. 1 (c). Such a structure has not been
observed by the author in the miracidia of any of the other species of schistosomes
studied by him so far. These ' shoulders ' are noticeable just at the places where
the posterior set of secretory glands open in the liberated miracidia.
The miracidium, after hatching out of the ovum, appears to spread itself out
somewhat, during which process it seems to be stationary. This enlargement is
perhaps due to the release of pressure to which it is subjected while in the egg.
Very soon it becomes active, swimming away vigorously in water almost in a
straight line till deflected by an obstruction in its course.
The miracidium (Plate XII, fig. 2), when killed with five per cent formalin
solution, is roughly almond shaped. Anteriorly, it has a nonciliated snout or
papilla with an oral opening at its apex. The oral opening leads into a short and
blind digestive sac, fully packed with refractile granules. The anterior secretory
gland, one on either side of the digestive sac, is rounded, bearing a long duct which
opens anteriorly at the base of the snout on each side. These glands are packed
with large oxyphilic granules. Each of them together with the duct is about twice
as long as the digestive sac. About the middle of the body, in the median line,
is situated a rounded compact structure, composed of a number of cells filled
with fine basophilic granules. This is the posterior secretory gland from which two
ducts, one on each side, appear to arise and each opens on a short papilla in the
region of the ' shoulder ' referred to above. There is a ring of nonciliated cuticle