Constitutional Vigor in Poultry Breeding. 



6og 



Strong Weak 



A. Barred Plymouth Rock 



Strong Weak 



B. White Plymouth Rock 



Weak Strong 



C. White Leghorn 



Weak Strong 



D. Silver Spangled Hamburg 



Weak Strong 



E. Buff Plymouth Rock 



Strong Weak 



F. Buff Orpington 



Fig. 2. — A, B, C, D, E and F. To show contrast in constitutional vigor in cockerels 

 of six varieties. 



20 



