Development of sporocysts of first and 
second generation. 
(Figs. 18—50) 
When an antenna of Planorbis olivaceus 
is examined shortly after the infection, the 
miracidium is seen stretched lengthwise under 
the skin; the intestine and the glands are in- 
distinct and seem empty but the vibrating la- 
mellae and the cilia of the external epithe- 
lium continue to play. Contractions and dis- 
placement of the miracidium are also percei- 
ved. Finally everything becomes quiet. The 
epithelium is cast off and there remains only 
an oval bcdy with thin membrane, in which 
the germinative cells multiply and become 
more distinct. 
(An antenna, cut off two days after the 
penetration of the miracidium, appeared oede- 
matous. Immersed in physiological saltsolu- 
tion and compressed by a coverglass, it be- 
came sufficiently transparent to permit the 
examination by an oil immersion lens. The 
sporocyst was stiJl extended lengthwise, but 
on its outer side there was a clear space in 
which the rests of the ciliated membrane 
were seen. The cilia themselves had already 
disappeared leaving only indistinct rests. The 
outline was now very fine and the two poles 
were equal, as the papilla, the gland- 
cells withs their ducts and the great vesicu- 
lar cells had disappeared. In the interior 
small granules, round bodies of nuclear 
aspect, vesicular elements and a few hyaline 
cells were seen in a protoplasmic mass wi- 
thout distinct structure. The four tubular ori- 
fices, with their ciliated membrane in lively 
movement, were still visible and continued 
so for at least five hours: also the ciliated 
epithelium of the antenna was well preserved, 
but after ten hours every movement had 
ceased; the epithelial cells of the antenna 
were detached and their cilia had dropped 
or disappeared.) 
After three or four days the secondary 
swelling ofthe antennae indicates the evolu- 
tion of the sporocysts. These simple or mo- 
niliform swellings increase in the first forth- 
night. About twenty days after the infection 
119 
they become pale and shrunken without dis- 
appearing altogether; therefore the infected 
snails may be recognized even after a long 
time. But it must not be forgotten that simi- 
lar lesions may be due to the parasitism of 
other trematodes. 
After several days the distended membra- 
ne of the sporocysts has become so thin that 
it is hardly seen; nor may it be stained in 
the flattened antenna. Crushing one of the 
swellings 5-6 days after the infection, one 
sees a large number of round masses, formed 
by small cellules with a central body ressem- 
bling a nucleus. Some of them occupy the 
swollen part of the antennae, while others 
escape by the rupture. Examination in colo- 
red sections offers no great advantage. 
A few days afterwards, the masses stre- 
tch, forming short secondary sporocysts 
that move about in the lymph ofthe anten- 
nae and for a short time in physiological 
solution. Constrictions are frequently seen, 
and seem toindicate a multiplication by trans- 
versal division. In water, they perish rapidly. 
In this period theemigration of the sporo- 
cysts towards the visceral sac begins. They 
are found there 20 days after the infection, 
forming very long and branched sporocysts 
containing oval masses, destined to the for- 
mation of new sporocysts or cercarias. In 
these the body is formed first, then appears 
the stem and finally the branches ofthe tail. 
The whole body is still covered by an epi- 
thelium with easily stained nuclei. Living 
and active cercariae appear only after a month 
and a few days. In other cases, due proba- 
bly to less favourable temperatures, new spo- 
rocysts are apparently formed. 
Cercariae with forked tail. 7). 
For some time past cercariae with 
forked tail have been known, though further 
evolution was ignored. They were considered 
as curiosites of no apparent importance. They 
are rarer in Europe than in warmer regions, 
where they constitute half of the easily found 
species. In Brazil, 1 know of four quite dis- 
tinct species found in different Planorbis 
