(Figs. 65-68) and of one observed in a Se- 
misinus. 
In 1913 MIYAIRI and SUZUKI published 
an important work in which they described 
the evolution of the Schistosomum japonicum. 
The cercaria was found in a fresh-water 
mollusk with a shell like those of the genus 
Bithynia. 1t was considered new and called 
Blanfordia or Katayama nosophora ROBSON. 
The description and the illustrations show 
that thecercaria has six large unicellular 
glands in the posterior part of the body. 
According to the authors they are formed in 
secondary rediae which, however, are really 
sporocysts. The percutaneous infection was 
proved by experiments on animals. 
The observations of the Japanese inve- 
stigators were confirmed and amplified by 
independent studies, made by LEIPER. The 
latter, as chief of a scientific commission, 
continued his studies in Egypt where former 
students, though observing many cercariae, 
had failed to recognise those belonging to 
Schistosomum. He found four cercariae with 
corresponding characteristics and was able to 
obtain adult schistosoms in animals, as well 
by cutaneous infection as by ingestion of 
cercariae. As hosts of Schistosomum haema- 
tobium, he indicated snails akin to Planorbis 
and Physa. 
Later on he concorded with the distinc- 
tion between Sch. haematobium and Mansoni 
giving Physopsis africana as principal inter- 
mediary host of the first and Planorbis Bots- 
syi as that of the second. 
Description of the cercariae of Schis- 
tosomum Mansoni. 
(Figs. 48 & 51-63.) 
The newly formed cercariae, found in 
great numbers in the viscera of infected snails, 
are covered, body and tail, by an epithelium 
with large and closely disposed nuclei, also 
revesting the suckers and making them stand 
out clearly. After this has been shed by a 
kind of moult, tke body becomes more trans- 
parent without showing its structure more 
clearly (Fig. 62). 
120 ——— 
Fresh preparations were fixed in osmic 
acid, others in formol and coloured by va- 
rious methods; segments of infected snails 
were stained with hematoxylin only, or follo- 
wed by eosin or VAN GIESON; thus I was 
able to verify the following details of struc- 
ture which are not easily seen by using one 
method only. 
The body of the moving cercaria shows 
the varied aspects, observed in other flukes 
and due to their extreme contractibility. In 
repose they assume the form of an egg with 
one end truncate. The greatest length is 0,14, 
the greatest width about 0,04- 0,05 mm. The 
tail shows a very contractile basal part, for- 
ming in repose an elongated cone; fixed to 
its truncate apex is a spindleshaped transver- 
se piece which can be folded in the middle, 
so as to form a prolongation of the basal 
part (fig. 60). This has a length of about 
0,27 and a (greatest) width of 0,03, each 
half of the transversal piece being about 
0,08 mm. long. Thus the whole length may 
attain nearly 0,5 mm. With good light, these 
dimensions are sufficient to show the statio- 
nary cercaria in the shape of a short white 
stroke. When swimming it appears in the 
very caracteristic form of an 8, due to the 
rapidity of its movement. 
The whole body, tail included, is trans- 
parent, slightly opalescent and covered with 
very minute spines. 
The body representing the earliest form 
of Schistosomum has two suckers, the oral 
one, with a diameter of 0,03 mm., being far 
larger than the posterior. Its shape is that of 
an ovoid with the anterior fourth cut off. 
Its musculary system is insignificant but the 
mouth and pharynx, situated at the posterior 
end may be drawn in the cavity and even 
reach the anterior opening. The movements 
of these parts are like those of the piston 
of a syringe and very striking. 
Just inside the exterior opening of the 
sucker there is a ring of 6 or more small 
spines which, together with the supporting 
part, may be everted and form a short ro- 
strum, Near their base open the excretory ducts 
of the abdominal glands, the secretion of 
