78 WORM PARASITES. 



fowls causing the disease ; the parent worms were 

 ruptured either in being picked up, or soon after, 

 the embryos thus set free at once entering the 

 tracheal tube. 



How this entrance takes place is not known : 

 whether by the self-conscious movements of the 

 embryo or by chance yet remains to be proved. 



"Walker has observed the embryos of this parasite 

 in Earthworms, and thus he says the fowls get 

 the disease. There is no reason to doubt that this 

 does often happen ; the embryos and eggs may, 

 and probably would, be taken in with the soil the 

 Earthworms devour. But this is no proof that the 

 Earthworm is an intermediate host of the Syngamus. 



Amount of Loss in Fowls, Sfc. 



Crisp says that half a million pullets are destroyed 

 annually in England. Wiesenthal estimated the loss 

 of Galling in the invaded areas he examined at 

 four-fifths. If not so great as this now in England, 

 the loss is still serious in some districts. 



Theories regarding the Development of the 



Gape-worm. 



Regarding the development of Syngamus trachealis 

 there seem to be three theories, each entailing an 

 intermediate host. The necessity of this intermediary 

 is now practically disproved. The three hosts sug- 



