Physiology of Reproduction in Domestic Fowl 341 



II Physiology of egg production within the race? 



A Variation in egg production. 



1 Intra-racial 1 in regard to each of the points enumerated under I 



2 Inter-racial j above. 



3 Mutation. 



4 Seasonal distribution of egg production. 



B Inheritance of egg-producing ability. Considered with reference to each 

 of the points enumerated under I above. 



1 In pure-bred lines. 



2 Under hybridization. 



C Evolution of egg-producing ability. 



1 Influence of selection. 



2 Egg production in the wild progenitors of domestic poultry. 



3 Fixation of egg producing ability as a racial character. 



III The influence of environmental factors {in the broadest sense) on the processes 

 enumerated above. 



1 Nutrition. 



2 Housing. 



3 Meteorological factors. 



4 Drugs. 



5 Other environmental agents. 



IF The relation of internal factors to, and their influence upon the processes enum- 

 erated under I and II. 



V Pathological and teratological cases relating to egg production. 



This outline, while not as extensive or complete as it might be 

 made, gives a fairly comprehensive view of the general scope of the 

 problem which forms the subject of the present investigation. 

 Each topic in the list suggests, of course, a whole series of problems, 

 but even to enumerate all these would take far more space than is 

 available here. All that is desired at present is that the broad 

 outlines of the general problem on which we are working shall be 

 clear to the reader. On account of the extent of the subject it is 

 necessary to publish the results of the work upon it in a series of 

 separate papers. The skeleton outline given above will serve as 

 a means of coordinating the separate papers, and making clear the 



' The general standpoint which regards variation, heredity and other factors of evolution as physio- 

 logical problems has been well set forth by Jensen ('07) and Jennings ('08). 



