CHAPTER XIII 



THE TAPEWORMS 



General Structure. — Even more 

 peculiar and remarkable in their 

 structure and life than the flukes 

 are the tapeworms. A mature tape- 

 worm is not an individual, but a 

 whole family, consisting sometimes 

 of many hundreds of individuals one 

 behind the other like the links of a 

 chain (Fig. 81). In some respects 

 the tapeworms are more degener- 

 ate than flukes, due to their in- 

 variably parasitic life in the digestive 

 tract of their hosts. Being continu- 

 ally bathed in semi-digested fluids 

 in the intestine they can readily 

 absorb food all over the surface of 

 their bodies, and have no need for a 

 digestive system of their own. The 

 digestive tract, therefore, is entirely 

 lacking, not even a vestige of it 

 remaining as an heirloom from less 

 dependent ancestors. 



In general form the majority of 

 tapeworms are very long tapelike 

 organisms which attach themselves 

 to their host's intestinal walls by a 

 "head" or scolex at what is really 

 the posterior end of the chain of 

 segments. This scolex is furnished 

 with suckers and often hooks as well '^^Zli'chklge in^sfzeTf'^pro^giot- 



(Fig. 82). ■ Next to the head there tids, and irregular alternation of 



is a narrow region 

 which continually gi'ows and forms 

 segments as it grows, each new segment thus produced pushing 

 forward the segments previously formed. This process eventu- 



231 



Fig. 81. 



Beef tapeworm, Tcenia 



2 



ci in sides of genital apertures. (After 



or necK g^j^^g^ 



