I08 MAINE AGRICULTURAL EXPERIMEXT STATION. I909. 



tion, or (c) the embryo died late in incubation, or (d) hatched 

 a good or a poor chick. 9. The date at which the egg hatched 

 or failed to hatch. 10. The number of eggs which had been 

 laid by the hen which produced this given egg before it was 

 laid. II. The pedigree of this hen. 



Since these records have been taken for every egg put into 

 the incubators it necessarily means that they were taken for 

 every bird in the breeding pens during each hatching season. 

 Both in 1908 and 1909 the female birds which were used as 

 breeders were chiefly pullets but they also included a number 

 of yearling and older hens which in the past had made high 

 egg records and were on that account put into the pens as 

 breeders. In any study of such problems as those here under 

 discussion it is necessary that the material be homogeneous. In 

 consequence pullets and old hens must be treated separately. 

 The discussion which follows deals with pullets except where 

 a specific statement to the contrary is made ; namely, birds 

 hatched either in the spring of 1907 or 1908. 



Furthermore it is necessary in a discussion of these matters 

 that all individual birds included shall have had an equal chance 

 to produce eggs and to have them fertilized and incubated. 

 That is to say, only birds should be included in the statistics 

 which make a complete record for the whole hatching season — 

 from February to June. For practical and experimental rea- 

 sons it was found desirable in the 1908 work to withdraw a 

 number of breeding birds in the course of the season and sub- 

 stitute others in their places. Both the withdrawn and the 

 substituted birds are excluded from the present statistics. 

 Leaving these various classes of birds out of account there 

 remain no pullets which made complete records for the hatch- 

 ing season from February 8 to June lo, 1908. In the 1909 

 breeding season there w^ere 87 pullets and 58 yearling hens 

 (hatched in 1907) which made complete records for the sea- 

 son extending from February i to May 17, 1909. In both 

 years only Barred Plymouth Rock birds are included in the 

 statistics. 



A word should be said regarding the conditions under wdiich 

 the breeding was done. For the breeding investigations which 

 the Station has under way it is absolutely necessary to know 

 the male as well as the female parent of each chicken hatched. 



