136 MAINE AGRICULTURAL EXPERIMENT STATION. I9II. 



used to designate it is the important thing. That condition was 

 as described. 



It amounts to a truism to say that it is one of the strongest 

 and most ancient of breeding traditions that inbreeding is in 

 and of itself harmful, and inevitably results in deterioration. 

 This being so it is clear that a possible interpretation which 

 demands careful attention is that the real reason for the failure 

 of the mass selection experiment to produce increased mean 

 annual production was to be found in the blighting effect of 

 the inbreeding or narrow-breeding (as one chooses) which had 

 been practiced. The deterioration from this cause would be 

 held, on this view, to balance or offset the potential gain as- 

 sumed to have resulted from the selection. 



It seemed very important at the outstart of the new period 

 in the breeding work at this Station, to test carefully the valid- 

 ity of this interpretation. In order to do so the experiment to 

 be described was planned and carried out in 1908 and 1909. 

 The essential point to this experiment was to compare in respect 

 to egg production the offspring of two sorts of matings. In 

 one set of these matings both the male and female mated 

 together were from the Station flock and might be very closely 

 related (even brother and sister). In the other set of matings 

 the female in each case was from the Station flock but the male 

 was a pure-bred Barred Rock cockerel purchased from one 

 or another among the then more or less prominent breeders of 

 this variety in the eastern United States. It will be seen that in 

 the first case the progeny of the matings represent the continua- 

 tion to the full degree of the narrow breeding practiced during 

 the preceding 9 years. In the second case the progeny represent 

 the widest breeding possible. That is, the male and female are 

 absolutely unrelated and come from entirely distinct strains. If 

 the narrow breeding during the selection experiment was really 

 inimical to high egg production, and brought about deterioration, 

 it would be expected that progeny from parents of absolutely 

 unrelated "blood" would show marked superiority to those from 

 a continuation of the narrow breeding. The maximum effect 

 in the way of rejuvenation from "out-crossing" should show 

 itself here. 



In carrying out the experiment 8 Barred Rock cockerels 

 were purchased in the early spring of 1908 from as many 



