THE INCUBATION OF HENS' EGGS 



193 



Time of Holding Hatching Eggs. — Holding eggs for incuba- 

 ting purposes is a necessary evil to be practised as little as 

 possible. Two weeks is generally considered as the outside 

 limit of holding eggs under the very best conditions that will 

 give satisfactory hatching results. Waite' found, as shown 

 in Table XXVII, that the percentage of eggs not hatching 

 showed a, fairly consistent increase for all periods longer than 

 one week. 



Fig 96 



A Ki-apliic pre^entiitiori of Tal.le XXVII. (.M'tcr Waite ) 



Temperature for Holding Hatching Eggs.— The belief that 

 the earlier the development that is under way at the time of 

 laying is checked, the better are the chances of holding eggs 

 successfully for hatching, has led to the general practice 

 among poultrymen of gathering the eggs often during the 

 incubating season and putting them in a cool place. 



Edwards,- as the result of a series of comprehensive experi- 

 ments, has fixed the physiologic zero of the hen's egg at a 

 temperature lying between 20° and 21° C. This is the practi- 

 Ccal equivalent of saying that an egg will start to incubate 

 at a temperature lying between 68° and 70° F., and that to 



Maryland ISuUetin, No. 2.33. 

 ■ American Journal of Physiology, vol. vi, No. 3.5. 



13 



