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. If the 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 a sheep. The 

 heads may also bud forth from the outer as well as the inner 

 surface of the cysts, or brood-capsules, as they are called. 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 T ^ of an inch in diamter, and then generally coil- 

 tain only three or four heads. 



Each of the oval heads is a hollow sac, which contains the 

 real head of the young tape-worm turned in like the finger of 

 a glove, just as the heads are turned inward in the ccenurus 

 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 he.ads shown 

 in Figure 68, owing to the partial transparency of the mem- 



