PLA TYHELMINTHES 



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 



Fig. 75. — a, Bilhania haematdbia, the thin female in the gynoecophorio canal of the 

 stouter male, x 15 (after Leuckart). h, 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 hy Leucochloridium, 

 nat. size, d, Leucochloridium removed from the tentacle, nat. size (After Zeller). 

 e, Bucephalus polymcrphus, highly magnified (after Ziegler). /, 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 



