Outlines of zoology . Fig. 100.—Life history of Tania solium.—After Leuckart. I. Six-hooked embryo in egg-case; 2. proscolex or bladder-wormstage, with invaginated head ; 3. bladder-worm with evaginatedhead ; 4. enlarged head of adult, showing suclters and hooks ;S- general view of the tape-worm, from small head and thinneck to the ripe joints; 6. a ripe joint or proglottis withbranched uterus (cf. Fig. 99); all other organs are now lost. When man unwittingly eats measly pork—that is, porkinfested with bladder-worms—an opportunity for further>3 194 UNSEGMENTED WORMS. development is afforded

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Outlines of zoology . Fig. 100.—Life history of Tania solium.—After Leuckart. I. Six-hooked embryo in egg-case; 2. proscolex or bladder-wormstage, with invaginated head ; 3. bladder-worm with evaginatedhead ; 4. enlarged head of adult, showing suclters and hooks ;S- general view of the tape-worm, from small head and thinneck to the ripe joints; 6. a ripe joint or proglottis withbranched uterus (cf. Fig. 99); all other organs are now lost. When man unwittingly eats measly pork—that is, porkinfested with bladder-worms—an opportunity for further>3 194 UNSEGMENTED WORMS. development is afforded Stock Photo
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Outlines of zoology . Fig. 100.—Life history of Tania solium.—After Leuckart. I. Six-hooked embryo in egg-case; 2. proscolex or bladder-wormstage, with invaginated head ; 3. bladder-worm with evaginatedhead ; 4. enlarged head of adult, showing suclters and hooks ;S- general view of the tape-worm, from small head and thinneck to the ripe joints; 6. a ripe joint or proglottis withbranched uterus (cf. Fig. 99); all other organs are now lost. When man unwittingly eats measly pork—that is, porkinfested with bladder-worms—an opportunity for further>3 194 UNSEGMENTED WORMS. development is afforded
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Image ID: 2AJ0BD9
Outlines of zoology . Fig. 100.—Life history of Tania solium.—After Leuckart. I. Six-hooked embryo in egg-case; 2. proscolex or bladder-wormstage, with invaginated head ; 3. bladder-worm with evaginatedhead ; 4. enlarged head of adult, showing suclters and hooks ;S- general view of the tape-worm, from small head and thinneck to the ripe joints; 6. a ripe joint or proglottis withbranched uterus (cf. Fig. 99); all other organs are now lost. When man unwittingly eats measly pork—that is, porkinfested with bladder-worms—an opportunity for further>3 194 UNSEGMENTED WORMS. development is afforded. The bladder is lost, and is of noimportance, but the head or scolex fixes itself to the wallof the intestine. There it is copiously and richly nourished,and buds off asexually a chain of joints. As these joints are pushed by younger interpolated budsfarther and farther from the head, they become sexually HEAD. Fig. ioi.—Diagram of life history of Tarda solmm. First chapter : Tapeworm in man ; H., head ; PR., proglottides. Secondchapter: Free proglottis and egg-cases; «^., uterus; >r.«., genital aper-ture; embryo within the egg-case. Third chapter: Within the inter-mediate host, the pig; H., hexacanth embryo; p.sc, proscolex or bladder-worm ; m.f muscle of pig ; sc, scolex or head. mature. The ova are fertilised, apparently by spermatozoafrom the same joint; the joint becomes distended withdeveloping embryos. These ripe joints are liberated, theembryos are set free by rupture, and the vicious circle mayrecommence. Happily, however, the chances are manymillions to one against the embryo becoming an adult. The above history is true, mutatis mutandis, for many other tape-worms. The embryo grows into a proscolex or bladder, which buds off CESTODA. 195 a scolex or head, which, in another host, buds off the chain oiproglottides.As it is virtually the same animal throughout, the life history