282 
ROT IN SHEEP. 
to examine it, we find to be exceedingly complicated, the two 
sexes being blended together in one individual, as we find in 
many other creatures. It is not, however, to be considered as 
an hermaphrodite—that term is not strictly applicable to it— 
but it is a bi-sexile creature, the two sexes being distinct, 
separate, and perfect. In whatever animal you meet with these 
entozoa, they are precisely alike in this respect. We have here 
a representation of the generative system, by which we see that 
the male organs are contained in the centre of the body, and 
that the female organs have their origin at the periphery, 
uniting in two ducts which meet in the middle, where the true 
uterus or womb is located, and which is here represented as 
being filled with a great number of eggs. After the eggs are 
perfected they escape from an opening which is very near to 
the central sucking disc. With regard to an appendage near 
this opening, and which is sometimes protruded, and some¬ 
times retracted into the body, it has been supposed to be an 
intromittent organ or penis, and its existence in all these crea¬ 
tures would rather seem to show that although they are bi- 
sexile, it is not improbable that copulation takes place between 
them. We have a similar instance with regard to snails, 
which are bi-sexile, and it is well known that they are 
furnished with an intromittent organ as well as a vagina, and 
that the intromittent organ of the one extends into the vagina 
of the other ; and it is not improbable that this takes place 
also with the fluke, but this point is not at present fully ascer¬ 
tained. The sucking disc, as it is called, which is seen on 
the ventral part of the animal, is simply an organ which evi¬ 
dently performs the office of holding the creature on w hen it 
is traversing the biliary ducts, forming a kind of focal point. 
Thus it can travel onwards and insinuate itself into the minute 
ramifications of the ducts. Nor is it improbable, if copulation 
does take place between tw r o of them, that the sucking discs 
approximate to each other for the purpose of contact during 
that period. If you take any fully developed fluke, it would be 
perfectly impossible for any one to say w hat number of ova 
such a creature contains; but there is one circumstance 
especially, which renders the ova interesting to us, namely, 
that if we examine them never so carefully, and any number 
we please, those that have been naturally expelled from the 
creatures as w'ell as those that are contained within them, we 
shall find that there never exists within these ova anything of 
the outline of the young fluke. This fact being established, 
it is evident that, in order for the fluke egg to produce ulti¬ 
mately a young fluke, the germs contained within it must pass 
through a series of transmutations—that either metamorphoses, 
