194 



UNSEGMENTED "WORMS." 



development is afforded. The bladder is lost, and is of no 

 importance, but the " head " or scolex fixes itself to the wall 

 of 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 buds 

 farther and farther from the head, they become sexually 



FIG. 101. Diagram of life history of Tania sotfttm. 



First chapter: Tapeworm in man; ff., head; PR., proglott ides. Second 

 chapter: Free proglottis and egg-cases; tit., uterus; &.a., 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 ; /., muscle of pig ; sc., scolex or head, everted in final host. 



mature. The ova are fertilised, apparently by spermatozoa 

 from the same joint; the joint becomes distended with 

 developing embryos. These ripe joints are liberated, the 

 embryos are set free by rupture, and the vicious circle may 

 recommence. Happily, however, the chances are many 

 millions 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 ofl 



