PLATYHELMINTHES 113 
the boring hooks of their larvae for a change of host; as some 
compensation they are amply endowed with organs of adhesion 
in the form of either hooks or suckers. They have further 
Fie. 75.—a, Bilharzia haematobia, the thin female in the gynoecophoric canal of the 
stouter male, x 15 (after Leuckart). 6, Distoma macrostomum, showing the 
digestive, and the greater part of the genital apparatus, with the cirrus pro- 
truded, x 30. c, Snail (Succinea), the tentacles deformed by Leucochloridium, 
nat. size. d, Leucochloridium removed from the tentacle, nat. size (after Zeller). 
e, Bucephalus polymorphus, highly magnified (after Ziegler). .f, Portion of a 
sporocyst containing Bucephali in process of developement, x about 50 (after 
Lacaze Duthiers). 
acquired the power of producing an enormous number of eggs, 
a necessary provision when the remoteness of their chance of 
hitting on the right host is taken into account; this power of 
propagation is further increased in many cases by the asexual 
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