THE TAPE-WORM. 159 



1. The cestoidea, which include the taenise or tape- 

 worms and the bothriocephalus, may in the adult stage 

 reach a very great length, at the same time keeping a 

 very narrow width. Thus the taenia solium, the common 

 tape-worm, is sometimes a hundred yards in length; it 

 then presents the appearance of a long ribbon formed of 

 numerous rectangular segments, somewhat longer than 

 they are wide, and joined end to end. Each of these 

 segments contains male and female organs, 

 and may be considered as an individual, 

 while the whole worm is regarded as a 

 colony of individuals arranged in a chain. 



However this may be, the first segments 

 are much smaller, and are more closely 

 pressed together, forming a sort of neck, 

 at the end of which appears what is called 

 the head, a small swelling that is not as HEAD OF TAPE . 

 large as the head of a pin, and that carries WORM, EN- 

 a double crown of thirty-two hooks and hJokJT'*, i 

 four suckers, arranged like a cross. The holes; s, first 

 hooks and suckers enable the creature to fix 

 itself firmly to the walls of the intestine in which it lives. 



The taenia has no digestive apparatus. The only ones 

 of its organs that have been studied with definite results 

 are those of the sexual apparatus. A large number of 

 eggs are produced, and when a segment is ripe it be- 

 comes detached and is carried out of the intestine. 



We have said that the tape-worm lives as a parasite 

 in the intestines of man, and it is by eating measly pork 

 that man acquires the unwelcome guest. In order to 

 understand this indirect transmission, we must under- 

 stand the mode of development of the creature, which 

 undergoes metamorphoses that are quite complicated. 



