INCUBATION 263 



ten ounces on each hundred average eggs, and on this basis the 

 proper loss of weight for any number of eggs is readily computed. 

 It should be understood that the shrinkage in natural incubation is 

 not uniform, and that equally good hatches would probably be ob- 

 tained on any evaporation between the 1 1 per cent observed at the 

 Ontario station and the 1 7 per cent observed at the West Virginia 

 station, possibly between wider limits, though it seems improb- 

 able that the limit could be moved much farther up or down without 

 affecting the result. When it is not convenient to weigh eggs, it is 

 advisable (especially for the novice) to run check lots of eggs under 

 hens, using two or more hens if possible, that the check may not 

 be invalidated by a poor sitter or by accident. A further advantage 

 in check hatching with hens is that a right amount of evaporation 

 does not necessarily insure a hatch, and that the results from the 

 hens afford checks on other points which may need investigation. 



Management of the incubator at hatching time. The excuses 

 for disturbing the hen at this time do not apply to the incubator. 

 From the time when the eggs are last turned and cooled (on 

 the eighteenth day) until the chicks have ceased hatching, it is 

 as well to let them alone. The temperature tends to rise at this 

 time, and may be allowed to go to 104 or 105, but if it runs 

 higher, the flame should be reduced. All chicks that are to hatch 

 should be out within twenty-one days (ducks, twenty-eight days) 

 from the time of the beginning of incubation, though the eggs of 

 large breeds may run a little longer. Eggs that have been run at 

 too low a temperature, or have been chilled, are likely to be delayed 

 and to give rather weak chicks. Such matters, and any other points 

 shown by the record which would affect the hatch, should be given 

 consideration in dealing with belated hatches. It is usual to leave 

 the young birds in the incubators from twelve to thirty-six hours 

 after the conclusion of the hatch. When the incubator is provided 

 with a nursery (under the egg tray) the birds are allowed to drop 

 into it, where they have more room and leave more room on the 

 tray for the late comers. 



Accounting for results. Consideration of results and the causes 

 affecting them should be made with some care after the hatch. 

 This is as important when the hatch is good as when it is unsat- 

 isfactory. When good results are obtained notwithstanding some 



