20 BULLETIN 817, U. S. DEPT. OF AGRICULTURE. 
with which young chickens can readily be infected by feeding the 
eggs of gapeworms taken from turkeys. In turkeys full-grown 
gapeworms commonly reach a length of 25 to 40 mm., but in chickens 
infected with material from turkeys the egg-producing adult rarely 
exceeds 15 to 20 mm. in length. 
Fic. 4.._Ascaris suum. Larva in liver of mouse 10 days after infection. Photomicrograph 
f of living specimen. Magnified. 
In the case of migrating Ascaris larve differences of size are no- 
ticeable in different species of host animals, if a comparison is made 
of larve taken from different animals at corresponding times fol- 
lowing infection. The following table has been compiled from the 
results of experiments on mice, guinea pigs, and rabbits: 
