134 PHEASANTS FOB COVERTS AND AVIARIES. 



as the l-250tli of an incli (Fig. 5). Many of the ova contain 

 fully -formed embryos. By whatever mode the young make 

 their exit from the shell, it is manifest that prior to their 

 expulsion they are sufficiently developed to undertake an 

 active migration. Their next habitation may occur within 

 the body of certain insect larvae or even small land mollusks ; 

 but I think it more likely that they either enter the sub- 

 stance of vegetable matters or bury themselves in the soil 

 at a short distance from the surface." 



Since the publication of this paper, the history of the 

 gapeworm has been very carefully studied by other observers, 

 whose investigations have been recapitulated in Theobald's 

 " Parasitic Diseases of Poultry." Mr. Theobald describes the 

 ova and embryos as escaping by the rupturing of the female's 

 body, which takes place, as a rule, after the worm has been 

 expectorated by the fowl or pheasant. Both eggs and 

 embryos, as suggested by Dr. Cobbold, take up their abode 

 in damp ground, that around the drinking vessels of the 

 fowls being a favourite locality. 



The eggs hatch in from seven to forty days, according 

 as to whether the surroundings are favourable or not. 

 These ova and embryos get taken up by the young birds 

 either off the ground or in the water; they then develop 

 into the worms in the tracheal region of the fowl. The 

 small embryo worms grow rapidly, soon become mature, 

 and the females unite permanently to the males. They are 

 often spread by one bird devouring the worms coughed up 

 by another, and they are conveyed from one area to another 

 by being carried by such wild birds as the starling and 

 magpie, which are both very largely infested with Sj/ngamus 

 trachealis. 



The theory that an intermediate host is necessary for the 

 hatching of the ova has now been entirely disproved. Young 

 fowls and pheasants quickly contract the disease when fed 

 on contaminated soil in which the ova are present. Breeding 

 pheasants on the same ground, as most gamekeepers know. 



