140 POULTRY PRODUCTION 



ceases. With the average period of profitable prothiction 

 but two years, the necessity for the abihty to renew 

 the tlock each year with a fair degree of certainty is 

 obvious. 



Assuming good vigor, actual infertility, by which is meant 

 the lack of a vital union between the sperm and the ovum, 

 is usually caused by sterility, or aversion on the part of the 

 sire, barrenness on the part of the dam, or by physiologic 

 selection. It is not to be assumed that because a particular 

 hen gives few or no fertile eggs she is worthless as a 

 breeder. It often appears that males have faA'orites in a 

 Hock with which they mate frequently wdiile there are others 

 that are never served. It happens less often that two inih- 

 viduals, which produce healthy chicks when mated with 

 other individuals, produce no fertility when mated together. 

 Such a condition is referred to as one of physiologic selection. 

 The remedy in each case is the making of a new mating or, 

 where feasible, alternating nuiles in the pen from day to day. 

 If ui)on mating with another male a female still returns 

 no fertility she may be assumed to be barren and useless. 



In the case of partial or total sterility on the part of a male 

 the low fertility of the eggs from all the hens mated with 

 him will necessitate his being discarded in self-defense. 



It would seem from the evidence at hand that infertility 

 in females of itself is not to be feared from the stand-point of 

 inheritance. It is rather an individual idiosyncrasy, highly 

 disappointing in present, but not serious in regard to future 

 effects upon offspring. In records furnished by Pearl and 

 Surface' it is shown that "There is no evidence that the 

 character 'fertility' of eggs (measured by per cent of eggs 

 infertile) is in any degree or manner inherited." Very much 

 more serious from the standpoint of progeny is the frequent 

 occurrence of "dead in the shell," by which is meant that 

 while the egg is fertile it fails to hatch. Pearl and Surface- 

 found that " The character hatching quality- of eggs (measured 

 by the per cent of fertile eggs hatched) is definitely inherited 

 in the female line and probably also in the male line." 



■ Maine Bulletin No. 168. ' ii,i,| 



