BREEDING POULTRY FOR EGG PRODUCTION. 1 35 



evident from Tables B and C as not to require further dis- 

 cussion. 



We come now to the consideration of the last point in con- 

 nection with artificial incubation. As was pointed out "above 

 (p. 127), if this had been the cause of the failure to increase egg 

 production during the mass selection experiment, it ought to 

 act as an equally efficient cause to prevent increase of egg pro- 

 duction by any other method of breeding. As a matter of fact 

 it did not so act, as is proven by the data given in Part IV of 

 this bulletin. Without any change whatever from artificial 

 methods of incubation or rearing it has been possible to isolate 

 and breed from the Maine Station stock strains or lines in which 

 high fecundity has been maintained during four generations at 

 least. If the reader will study the diagram on p. 168 (fig. 84) 

 remembering that during the zvhole period covered by the dia- 

 gram there has been nothing but artificial incubation and rear- 

 ing practiced he will find it difficult to believe that this factor has 

 influenced, either one way or another, the results of the breed- 

 ing experiments on fecundity at the Maine Station. 



INBREEDING. 



It has been pointed out above in the description of the mass 

 selection experiment that no "new blood" was introduced into the 

 flock during the course of that experiment. That is to say, 

 no new additions were made to the hereditary constitution of 

 the birds during that period. This certainly represents a condi- 

 tion of some degree of inbreeding, at least, in spite of the fact 

 that an effort was made never to breed close relatives together. 

 As a matter of fact, because of a lack of an adequate system 

 of individual pedigree records during this mass selection experi- 

 ment, it probably happened on several occasions that quite 

 close relatives were bred together. Whether or not this 

 occurred, it is certain that during 9 years only the "blood"* 

 of relatively few original individuals was represented in the 

 flock, and since all this breeding was in one line, the result 

 can certainly be regarded only as a narrow-bred flock. Whether 

 one chooses to call this "inbreeding" or not depends on his defi- 

 nition of the term. The biological condition and not the term 



* Meaning germ-plasm. 



