inheritance; of fecundity in domestic eowi,. 385 



111 view of all these considerations it seems certain that the 

 results obtained are not open- to criticism on the ground of the 

 time unit used as a measure of fecundity. 



Another matter which needs careful consideration is as to the' 

 possibility of unconscious bias having influenced the results 

 themselves. In other words, to what extent does the personal 

 ecjuation factor enter into this fecundity work? It can be fairly 

 said, I think, that there is less opportunity for unconscious bias 

 to affect the results here than in genetic work on most other 

 characters. The reason is because of the impersonal and objec- 

 tive character of the original records in the case of fecundity. 

 The original trap-nest records on which this whole study is 

 based were made by Mr. F. Walter Anderson. He had neither 

 knowledge of, nor interest in, the use of which any particular 

 record or set of records were tO' be put. He was solely concerned 

 to make as accurate record as possible of the laying of each in- 

 dividual hen. The system, of record taking used is such that it 

 was impossible for him to have any notion of what the total pro- 

 duction of any given bird up to a particular date had been. The 

 chance for bias or personal equation influencing results is ex- 

 cluded when, as in the present case, one person makes the basic 

 records, and has nothing whatever to do with their analysis, 

 while another person analyzes the data but has nothing directly 

 to do with their collection. 



Another safeguard on the results in this same direction, and also 

 in another, is found in the fact that birds belonging to the same 

 family (full sisters) were not given identifying numbers which 

 would make it possible to be certain or even to surmise that they 

 were sisters, without consultation of the pedigree records. The 

 numbering of the birds for identification each year was purely 

 at random and without any regard whatsoever to relationship. 

 Furthermore members of the same family were distributed at 

 random through the different pens and houses. No attempt is 

 ever made, from the day the chicks hatch, to keep the birds 

 from one family together. Indeed it is important that they be 

 scattered at random through the flock in order to insure uni- 

 formity of average environmental conditions. 



The writer has no desire to generalize more widely from the 

 facts set forth in this paper than the actual material experimen- 



