FERTIUTY AND HATCHING OF EGGS. Ill 



Our certainty on this point was gained through a change of 

 plan which was adopted in the 1909 breeding season. This 

 year the eggs were candled and sorted as before by Mr. Ander- 

 son. Then every egg which did not hatch was opened by the 

 writers, and the accuracy of the original candling result tested 

 by direct examination of the contents of the egg. This method 

 did two things. In the first place it made the 1909 records as 

 nearly absolutely accurate as it is possible to get them, and in 

 the second place it demonstrated to us the very high degree of 

 accuracy of Mr. Anderson's candling. 



In this discussion of the fertility and hatching of eggs it is 

 necessary to define the terms used with some precision, since 

 the term "fertility of eggs" in particular is used with rather 

 widely difl^erent meanings by different writers on poultry topics. 

 Considered from the strictly scientific standpoint there can 

 exist no such thing as "degrees of fertility." One very com- 

 monly hears and sees the statement made that particular eggs 

 are "strongly fertilized," or that such a cockerel, owing per- 

 haps to lack of constitutional vigor, causes the eggs to be 

 "weak in fertility," meaning that the embryos die in the shell 

 after a few days incubation. From the biological standpoint 

 an egg is either fertilized or it is not. The act of fertilization 

 consists essentially in the union of a single spermatozoon with 

 a single egg cell. If this union takes place the egg is fertilized. 

 If it does not take place it is not fertilized. Reducing this 

 consideration to a practical basis it means that the only logical 

 process is to record as infertile only those eggs which do not 

 start at all to develop, and to regard as fertile any egg which 

 begins development, even though development may stop in such 

 an egg within 24 hours after incubation begins. In taking the 

 records at the Station eggs are usually divided into four classes ; 

 namely, (a) those which are infertile; (b) those that are fer- 

 tile but in which the germs die soon (that is within two or 

 three days) after development begins; (c) those that die in 

 the shell at a later stage of development and (d) the eggs that 

 hatch. In all the discussion which follows it will be under- 

 stood that an infertile egg means one which docs not start to 

 develop because no spermatozoon has united with it, and that 

 hatching means the production of a liir chick from the egg. 



