242 ENTO-PARASITES AND HYGJENE. 



hundred and even goes beyond one thousand, the whole 

 chain having a length often yards and more. The head 

 or scolex is then the same as the nurse which produces 

 sexual individuals in a sexual way; it corresponds to the 

 redia, with the difference that the latter produces its 

 progeny inside, not outside, as the scolex of the tape- 

 worm. 



Bothriocephalus, "having suckers in its head," is in 

 shape like a cucumber seed and instead of sucking cups 

 has only two shallow furrows lying on the edge of tlte 

 head, also no hooks at all. A representative of this 

 species, Bothriocephalus latus, the broad tape- worm, is 

 found in man in places where fish are eaten raw. Its 

 joints are much longer than wide, and the worm itself 

 reaches a length of nine or ten yards, while the number of 

 its joints, which are distinguished by the rosette-shaped 

 ovarium, may run up to several thousands. Their eggs 

 are deposited in water ; the young embryos break 

 through by opening a little cover provided for that pur- 

 pose, and wander into an intermediate host, usually some 

 fish, where they lose such organs as they had developed 

 for this short period of their free life, — organs of loco- 

 motion, etc. 



Eggs of other cestods are not deposited, but must wait 

 until they get out of the host passively. The proglottids 

 reach the outside ; they may creep around, are brought 

 on the fields with the manure, and even if they should 

 dry up and die, the eggs which they contain are pro- 

 tected from the inclemencies of the season, from cold and 

 bad weather, by three or four layers of tissue, one of them 

 of especially great thickness. The form of the embryos 

 coming out of those eggs is very characteristic, so that 

 they may always be defined. They are small, globe-like 

 bodies, whose chief distinguishing features are six sharp 

 hooks with bent tops. These hooks are movable by means 

 of muscles and may be turned backward and forward. 



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