Days 2 4 6 6 10 



12 14 16 



Incubation Age 



IS 20 



Gms., 



22 



20 



19 



16 



14 



12 



10 



8 



6 



4 



2 







10 12 14 16 15 20 

 Incubation Ag<^ 



Fig. 52 b. 



