PARASITES OF ANIMALS. 93 
secondary or daughter cysts are formed inside the primary 
ones, and then others inside the secondary ones, within which 
the heads of the future tape-worms are formed by a peculiar 
budding process. Ifthe inner membrane of one of the small 
cysts be examined when quite fresh with a good microscope, 
there will be seen attached to it by means of slender stalks, 
numbers of small oval or rounded heads, looking something 
like fruit on a miniature plant, as shown in Figure 68, which 
shows a few of these heads attached to the inner mem- 
brane of a cyst from an echinococcus tumor of asheep. The 
heads may also bud forth from the outer as well as the inner 
surface of the cysts, or brood-capsules, as they arecalled. And 
these heads, either external or internal, may become changed 
by an enlargement of their bladder-like portion into new 
brood-capsules or cysts, and by budding produce other heads 
in their interior, as shown in Figure 69. The heads are found 
attached to the inner membrane of the primary cyst, together 
with secondary cysts or brood-capsules ; they occur in the same 
way in the interior of the secondary cysts, sometimes associ- 
ated with tertiary cysts, or grand-daughter vesicles; and also 
on the interior of the tertiary cysts. They sometimes appear 
even on the exterior surface of the secondary and tertiary 
vesicles. In all these situations they are similar in appear- 
ance and structure, and all are equally capable of developing 
into tape-worms in the intestine of a dog. Many of the 
smaller secondary and tertiary brood-capsules or cysts are not 
more than ;}, of an inch in diamter, and then generally con- 
tain only three or four heads. 
Each of the oval headsis a hollow sac, which contains the 
real head of the young tape-worm turned in like the finger of 
aglove, just as the heads are turned inward in the cenwrus 
and in the measles of pork, or the young of any other tape- 
worm. Often the head is turned outward, as is seen in one 
case in Figure 68, which shows well the four suckers around 
the head and the proboscis in the middle with its circle 
of hooks. These same organs can be seen indistinctly even 
when in their inverted position, as in the other heads shown 
in Figure 68, owing to the partial transparency of the mem- 
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