154 Bulletin No. 155.— 1913. 



from the mixture of black and white. The problem was therefore, 

 first of all, to produce this character de novo, as it were; or at least, to 

 obtain it as a result of mating fowls which, in themselves or in their 

 ancestry, were not known to possess the condition either in a fixed 

 or in a transitional state; in other words, in selecting the material 

 to be employed in the investigation, the use of Barred Pl^Tiiouth 

 Rocks and other barred breeds, as well as of their ancestors and their 

 derivatives, was to be scrupulously avoided. Secondly, the problem 

 was to so breed the birds manifesting the newly-produced character 

 that it should be made a permanent acquisition of the breed. 



As will appear in the following pages this end has in a measure 

 been reached,- — that is to say, a breed of barred fowl has been pro- 

 duced through the employment in breeding of factors found in birds 

 which manifested no somatic barring. But the nature of the results 

 secured is such as to call into question the truth of the very hypothesis 

 upon which the investigation was originally based. In other w^ords, 

 the question is now raised whether we are justified in considering the 

 type of barring revealed and studied in the experiments to be reported 

 in the light of a heterozygous character. The recently-devised 

 factor-hypothesis and its application to the principles of breeding 

 and laws of heredity, together with the theory of unit-characters, has 

 profoundly modified our views regarding the fundamental nature of 

 the things that are inherited. Thus, to discover a factor for barring 

 where it was not previously known to exist, and to produce such a 

 factor (or such a pattern) de novo by the bringing together of simpler 

 germinal elements, are manifestly two different operations. A dis- 

 cussion of the bearing of this consideration upon the results of the 

 present investigation may wtII be deferred until the experimental 

 data have been presented. It may be said here, however, that these 

 data may not be valueless notwithstanding that their significance now 

 appears to be different from that first assumed ; and the investigation 

 as a whole, though, perhaps not dealing with the actual "fixation" 

 of a heterozygous character as first surmised may still have the merit 

 of throwing new light upon one phase of the inheritance of the barred 



