FARM ANIMALS 321 



to be asked concerning eggs which are to be set is, 

 will they hatch ? A great difference in this respect 

 is noted in eggs from different hens and obtained 

 under different conditions. It becomes an impor- 

 tant problem, therefore, to determine as closely 

 as possible what conditions tend to lower the fertil- 

 ity of eggs and what conditions tend to increase 

 the fertility. We will first refer to conditions 

 which unfavorably influence the fertility of eggs. 

 If eggs are kept for a long time before incubating, 

 especially in tightly closed cases^ the fertility is 

 better preserved than if kept in the open air. This 

 indicates that eggs should not be too much exposed 

 when intended for incubation. A greater strength 

 of germ and higher fertility is observed in eggs 

 which are kept at a temperature of seventy degrees 

 F. before incubation than in those which are kept 

 at the lower temperature of fifty degrees F. After 

 a shipment of eggs from a breeder to a customer 

 it is of little consequence whether the eggs are set 

 or incubated at once or whether they are allowed 

 to rest for a few days. A slight difference is 

 perhaps in favor of not resting the eggs. The 

 question is frequently asked also how soon eggs 

 become fertile after mating begins and has been 

 determined by experiments as being not longer 

 than forty hours. That is eggs laid two days 

 after the cockerels are placed with the hens are 

 likely to be fertile. Eggs continue to be fertile 

 for at least two weeks after the cockerel has been 

 removed. There is no difference in the fertility of 

 eggs of different shapes. In a comparison of 

 twenty-five normal eggs with long eggs and roundish 

 eggs the fertility and strength of germs appeared 

 to be almost identical. Close confinement of hens 

 exercises a strong influence on the fertility of eggs. 



