12     THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, I.

The comparison of the flame cell formulae of both at once suggests that the
cercaria of S. spindalis and that of the nasal schistosome are two different entities
and naturally the adults that develop from these two should also be different. It
is interesting to note that Sewell [1930] in his classification of the Apharyngeal
Brevifurcate Distome Cercariae, places Cercariae Indicae XXX in his Group I,
along with S. haematobium, S. japonicum and S. mansoni, in which the cercariae
have three pairs of flame cells in the body and one pair in the tail. In his Group II,
which shows the first step in evolution in the flame cell pattern, he places the
cercariae of S. spindalis in which the posterior flame cell in the body is an additional
one. Hence there are four pairs of flame cells in the body and one pair in the tail
in this group of cercariae.

The author infected over 40 clean Limnea leuteola (Lamarck) and Planorbis
exustus (Deshayes) with miracidia of nasal schistosomes from experimental calves in
April 1933. The mortality in among those snails was high and only about six
Limnea and 14 Planorbis survived at the end of seven weeks and of these two
Limnea and one Planorbis were found to discharge Cercariae Indicae XXX. This is
another piece of confirmatory evidence in the life-history of the Nasal Schistosome.
A section of the digestive gland of one of the infected snails is seen in P1. I,
fig. 4.

        EXPERIMENTAL INFECTION AND INCUBATION PERIOD.

The cercariae chosen for infection were concentrated and enumerated according
to the method adopted by Fairley and Mackie [1930]. Of the three calves selected
for infection, calf No. 410 was drenched with 60,000 cercariae, calf No. 411 was
infected through the mucous membrane of the nose with 60,000 cercariae, and the
third. No. 409, was infected with 15,000 cercariae through the nasal mucous mem-
brane and 30,000 cercariae by drenching. Rao [ 1933 ] has already published a
preliminary report on this experimental infection and it is enough to say here that the
calf No. 411 showed typical ova and live miracidia in its nasal discharge in 84 days
after the first date of infection, calf No. 409 showed them in 88 days and calf
No. 410 took 100 days to show them in its nasal discharge. Hence the period of
incubation appears to be about three months. This finding in experimental calves
agrees with what Rao [1932 ] said after analysing the histories of naturally infected
animals in Nammiandal village near Tiruvannamalai. It is seen that the calf
drenched with cercariae took a longer time to develop the disease and at the same
time the attack was a mild one. The other two calves, on the other hand, showed
severe symptoms of the disease though calf No. 409 got a smaller dose.

In another set of experiments two calves were infected with large numbers of
cercariae of S. spindalis. One calf No. 458 was infected only through the nasal