26 
consists of a cephalic portion, which is extremely motile ana w 
the rest of the young worm by a ridge; 
situated an opening through which the 
next generation (cercariae) escapes. The 
posterior portion of the worm is provided 
at about the border of the third and last 
fourths of the body with two projections. 
There is a mouth with phartmx situated 
at the anterior extremity, the jtharynx 
leading into a simple blind intestinal sac. 
The redia, as well as the sporocyst, may 
be looked upon as a female organism, and 
in its body cavity are found a number of 
germ cells, which develop into individuals 
of the next generation known as — 
(f) Cercarise (figs. 28-30). — These or- 
ganisms are quite similar to the adult 
parasites into which they later develop. 
The body is fiat, more or less oval, and 
provided with a tail inserted at the pos- 
terior extremity. The oral sucker and 
acetabulum are present as in the adult, 
but the intestinal tract is very simple; on 
the sides of the body are seen two large 
glands, but the complicated genital organs’ 
of the adult are not visible. The cercaria 
leaves the redia through the birth open- 
ing, remains in the snail for a longer or 
carise. x 150. (After shorter time, or passes out of the body of 
Leuckart, 1889, p. 2/0. snail and swims around in the water. 
After a time it attaches itself to a blade of 
hich is defined from 
under the latter is 
Common Liver Fluke, 
with developed cer- 
fig. 130.) 
grass (fig. 29) or some other object, and forms a cyst around 
itself with material from the large glands, at the same time 
Fig. 23. — Free cercaria 
of the Common Liver 
Fluke, showing two 
suckers, intestine, 
large glands, and tail. 
, After Leuckart. 1889,' 
p. 279, hg. 137.) 
Fig. 29. — Portion of a grass stalk ivith three encapsuled cercarise 
of the Common Liver Fluke (ihsefo^a ^epan'm). x 10. (After 
Thomas, 1883, p. 291. fig. 13.) 
losing its tail. -It now 
remains quiet until swal- 
lowed by some animal. 
Then upon arriving in 
the stomach — <)f a steer, 
for instance — the cyst 
is destroyed, and the 
Fig. 30. — Isolated encysted 
cercaria of the Common 
Liver Fluke. x 150. 
(After Leuckart, 1889, p. 
286, fig. 142.) 
young parasite wanders through the gall ducts, or, as some believe, through the 
portal veins to the liver, where it develops into the adult hermaphrodite. 
