60 



PART V. 



Development of the Embryo into the Tcenia. 



HAVING thus far described the anatomical characters 

 of the Taeniae and their embryos in their different 

 stages of development towards the perfect state, as 

 also the different species of the human cestoidea, it 

 would not be amiss, before leaving the subject, to fol- 

 low the different steps of their transition towards the 

 perfect state. 



It has already been shown, that the eggs are con- 

 tained in the proglottides, and that these are thrown 

 off in the faeces. The ova are extruded from the ripe 

 proglottides, even while in the intestine of the bearer 

 of the tapeworm ; but here they are never hatched, 

 for the reason that they do not find provisions suitable 

 for their development These ova, from the tough, 

 resistant nature of their shells, we have seen, are 

 admirably calculated to withstand injurious influences, 

 even after their containing proglottis has died and 

 undergone decomposition. They find their way into 

 the intestine of their future host, usually through the 

 medium of food and drink: the shell is ruptured, 

 partly by the act of mastication, and partly by the 

 solvent action of the gastric juice, and the embryo is 

 set free. As before mentioned, the embryo is fur- 



