IMPROVING EGG PRODUCTION BY BREEDING. 219 



indicate to the poultryman that at bottom the foundation of a 

 great many of these differences in laying ability with which he is 

 familiar is heredity. But how? And under what limitations? 

 For plainly this is not a simple matter. If it were, none of our 

 hens now would ever lay less than 200 eggs per annum, except 

 in the case of remote back woods regions, where the gospel of 

 the trap-nest had not yet penetrated. Trap-nest selection of 

 high preducers has opened the eyes of the poultryman to one 

 thing certainly, even though it may have obscured his vision in 

 other directions. This thing which is clearest is that all high- 

 producing hens are not equally capable of transmitting this 

 valuable quality to their progeny. So that while it may be per- 

 fectly certain that the difference between a 200-egg producer 

 and a 50-egg producer is in some way or other an hereditary 

 diff'erence, we shall not get far towards a practical utilization of 

 this fact until we know something more about its nature. 



So, then, the first essential step to be taken towards the im- 

 provement of egg production by breeding is to find out the way 

 in which variations or differences in producing ability are inher- 

 ited. For some six years past considerable attention has been 

 devoted to this problem, with results which have been set forth 

 in detail in a series of papers from the Biological Laboratory of 

 the Maine Agricultural Experiment Station. Of the more recent 

 of these papers is Bulletin 205, M^hich has the title "The Mode of 

 Inheritance of Fecundity in the Domestic Fowl." This bulletin 

 is technical in character. It was not written for the poultryman 

 but for the professional student of genetics. On this account it 

 has apparently not been quite clearly understood by some poul- 

 trynien, and the results and conclusions have, in some cases, been 

 misinterpreted. It will be the endeavor here, as briefly as possi- 

 ble, to make clear the essential results of these studies. 



Facts about Inheritance of Fecundity. 



First as to the facts : The following are simple statements of 

 the actual results, obtained in trap-nesting Barred Plymouth 

 Rocks and Cornish Indian Games, and all possible sorts of 

 crosses between these breeds, over a period, collectively, of nearly 

 fifteen years. The total number of birds involved in these trap- 

 nesting operations has been large, aggregating, all told, between 



