104 BOARD OF AGRICULTURE. 
with an ordinary lens. These tubes commence in fine, rootlet- 
like branches, with rounded and closed ends, but the small 
branches constantly unite into larger trunks, which in turn 
all unite into one main trunk, running along the middle line 
of the body, and this terminates in an external orifice at the 
- posterior end. The use of this system of tubes is to remove 
the waste materials from the body. It may therefore take 
the place both of the kidneys and liver of the higher animals. 
There is no blood circulation and no true blood in these 
animals. 
Development. 
The fluke is a very prolific creature. Prof. Leuckart esti- 
mates that the ovaries may at any one time contain 45,000 
eges. The number of broods that they produce is not known. . 
The eggs that are discharged pass out of the intestine of the 
sheep, or other animal in which they live, with the excre- 
ment. Those that get into water or moist places hatch after 
several weeks, producing minute conical embryos, which are 
covered with vibrating cilia or lashes, by means of which 
they swim freely about in the water. In this state the em- 
bryo is ;4, of an inch long and 35 of an inch broad at the 
larger end. The cilia are psgz of an inch long. 
In a few days the external skin, with the cilia, is cast off, 
and after that the embryos are obliged to creep about, instead 
of swimming. Its farther development has not been traced, 
but it probably has a history similar to that of other species 
of flukes of which the entire history is known. Therefore it 
is supposed that the young embryos, above described, attach 
themselves to the bodies or enter the tissues of the fresh- 
water spiral snails, such as Limnea and. Physa. In this 
situation the form probably changes, and they become the so- 
called “ nurses,” and then a brood of larve of another form 
is developed in their interior, by a process of internal budding. 
These larve are provided with a tail and have a form some- 
what resembling minute tad-poles. In this state they are 
known as cercarie. They are finally discharged from the 
body of the ‘nurses,’ and escaping from the snails, may 
again swim actively about in the water, by means of 
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