54 BOARD OF AGRICULTURE. 
from the enclosing proglottid after the latter has been dis- 
charged from the animal that nourishes the parent tape-worm. 
The eggs usually escape by the bursting of the integument of 
the proglottid, owing to their increase in size, as the embryos 
develop within them. While attached to the tape-worm the 
successive joints are connected together by longitudinal tubes 
or ducts that pass through the entire length of the worm, gen- 
erally one near each edge of the joints. These are connected 
together by transverse tubes in each end of the successive 
joints (Figure 54). 
The reproductive organs occupy variously branched and 
ramified cavities in the interior of the joints, communicating 
by ducts with the external male and female organs, which are 
placed side by side, either on the edge of each joint, as in 
Tenia, or in the middle of one side, as in Bothriocephalus. 
The remainder of the joint is composed of a firm, more or 
less solid tissue. 
All the species of this order undergo remarkable metamor- 
phoses ; the larva living in one animal must be swallowed by 
another before it can become mature. 
II. Trematopes. (Flukes). 
This order includes a great number of more or less flattened 
worms, of which the “ fluke,” frequently found in the liver of 
sheep, causing the “ rot,” isan example (Figure 73). 
The body is generally broad and more or less oval, some- 
times elongated, but never divided into distinct joints. On 
' the lower side there is usually one or two prominent suckers, 
and sometimes several. There is a small mouth on the lower 
side, usually near one end, but no head. The mouth com- 
municates with a small, dilated cesophagus or stomach, and 
this with a more or less. branched and subdivided, sometimes 
arborescent, intestine, the branches ending in closed tubes or 
blind-sacs. Another system of branched and often much sub- 
divided tubes arises in the more or less solid tissues of the 
body. ‘These tubes are at first small, like rootlets, but grad- 
ually uniting into larger and larger branches, finally empty 
their contents into one or two main trunks, which open ex- 
ternally by one, or sometimes two orifices, near the posterior 
end of the body... This Js. falled, thes water-vascular system, 
