1916 ITURBE and GONCALEZ report 
that the host of Sch. M. in Ve- 
nezuela is Planorbis guadelopen- 
sis. 
1917 It is shown that some of the bra- 
zilian foci depend on Pl. centi- 
metralis and that Pl. guadelou- 
pensis also occurs. 
1918 The host of Sch. Spindale is disco- 
vered by GLEN-LISTON and 
SOPARKAR. 
Descriptive Part. 
The genus Schistosomum. 
(Figs. 1-8), 
The genus Schistosomum comprises dif- 
ferent species of blood flukes which posses 
an Oral and an abdominal sucker and were 
therefore at first included in the genus Dis- 
toma, now usually latinized Distomum. This 
genus is now subdivided in many others for- 
ming the family Distomidae. Sch, is distin- 
guished from most of them by having the two 
sexes distributed on two individuals instead 
of having them united in one. Another cha- 
racteristic is the habitat in the blood vessels 
to which these flukes are well adapted. 
Similar characters are found in a few 
more genera, allied and only recently sepa- 
rated. They form a sub-family which may be 
called Schistosominae. 1 quote the genera 
Bilharziella and Ornithobilharzia, observed 
in birds 4). 
Sexual dimorphism is very marked in 
Schistosomum. The male has a flattened and 
rather wide body, well developped muscles 
and pointed skin scales which assist it in hol- 
ding its place ayainst the blood stream; the 
female has a filiform body like a nematode; 
her muscles are weak and the scales are either 
absent or very small, 
After the cephalic part the body of the 
male widens out, though the lateral parts 
are not flat but inwards curled, thus consti- 
tujing the canalis gynaecophorus which gene- 
rally contains one, rarely two or more fema- 
les. The genital system is reduced to a sub- 
114 
divided testis (sometimes followed by a vesi- 
cula spermatica) and an excretory duct; there 
is no cirrhus. 
The female has a corpus vitelligenum, an 
ovary and a long tube corresponding to ufe- 
rus and vagina. A small segment which con- 
tains the first (and sometimes only) comple- 
tely formed egg, may be called ootype. 
In both sexes no pharyngeal or oeso- 
phageal bulb exists and the intestine is first 
double and afterwards simple, in varying 
extent. 
(There are three species living in man 
and five more found in domestic animals, all 
of them easily distinguished by their eggs. 
The human parasites also Occur in apes and 
rodents (spontaneous or experimental infec- 
tion), while Sch. japonicum is also found in 
most of the domestic animals). 
Description and differential caracters 
of Schistosomum Mansoni. 
(Fig. 1-8, 15.) 
The anatomy and morphology of Sch. 
M. were studied by the discoverer and also 
by LEUCKART, R. BLANCHARD, CHATIN 
and FRITSCH before 1888; the results were 
discussed by R. BLANCHARD in 1889 and 
by LEUCKART in the second part of his 
classical treatise, in collaboration with LOOSS. 
The problem might have been practically 
exhausted, if the authors had worked on one 
species only, (and not with a mixture of two) 
or only on the form found in the urinary 
system. For this reason the descriptions have 
only a relative value and ought be corrected 
for each of thetwo species, confounded under 
the name Sch. haematobium. 
The differences were already indicated 
by PIRAJA, FLU, HOLBORN and other 
authors who studied the american species, 
but, as they had no occasion to compare 
fresh specimens of the other species, the 
value of some differential caracters might have 
remained somewhat doubtful; but ¡LEIPER 
who ultimately had occasion to compare 
both species in Egypt, quite confirmed the 
correctness of the most important characters 
