142 



MANUAL OF ZOOLOGY 



SECT. 



Insect. This transference of the hexacanth embryo to the 

 second host is a passive migration, not an active one, as in 

 the case of the ciliated embryo of the Trematodes, the egg 

 being received into the enteric canal of the second host with 



FIG. 71. Development of Tape-worm. A, hexacanth embryo ; B, Proscolex ot 

 Tcenia saginata ; C E, stages in the formation of the scolex of the same ; C, 

 the invagination before the hooks and suckers have become developed ; D, after 

 the appearance of the hooks and suckers ; E, partly evaginated ; F, fully 

 evaginated scolex of T. solium with caudal vesicle ; G, scolex of T. serrata 

 with the remains of the vesicle ; H, young Tape-worm of T. serrata. (After 

 Leuckart.) 



the water or food. The digestive fluids of this second host 

 dissolve the egg-shell and set free the contained embryo, 

 which bores its way by means of its hooks to some part of 



