No. 614] 



EGG PRODUCTION 



69 



frequently encountered, but each is used very loosely. 

 The use, either of the term ' 'higher producer" or ''low pro- 

 ducer" without qualifications of any sort can scarcely he 

 considered sufficiently precise. Unless qualified by the word 

 annual, the term "high producer" in this paper will be un- 

 derstood to refer to the winter record only. Pearl ('12) 

 has defined a high producer as a bird that lays over 30 

 eggs during the winter, a mediocre producer as one that 

 lays during the winter but that lays fewer than thirty 

 eggs, while a zero producer does not lay at all during the 

 winter. As will appear later, the use of the numerical 

 value of the record as its sole characteristic is insuffi- 

 ciently precise. The term "true mediocre producer" will 

 be used to denote a mediocre producer in the sense 

 (Pearl's) explained below, while the term "mediocre 

 (under 30 eggs) producer" will be used elsewhere. 



The Influence of External Factors.— A brief consid- 

 eration of the relation of external factors to egg pro- 

 duction is necessary before considering internal factors. 



External factors may be divided into two classes : first 

 those that operate rather directly upon egg production, 

 and secondly those that operate indirectly, through their 

 influence on the organism as a whole. 



Under the head of direct factors should be mentioned 

 housing, climate, food, general care, etc. It should go 

 without saying that the birds must be properly fed and 

 kept under conditions generally recognized as suitable 

 for maximum egg production. It is not yet clear, how- 

 ever, that the optimum conditions are fully known, or 

 that they can be obtained at will, for with the present ap- 

 pliances for keeping poultry, only the crudest sort of 

 approximation can be made toward securing a uniform 

 environment. For example, one is never certain with 

 open-front houses that a draft may not strike one portion 

 of the flock, while on the roosts, but not another. There 

 are many little things of this sort which can not at pres- 

 ent be controlled, nor is it definitely known in what way 

 these "little things" influence egg production. Some 



