134 MAINE AGRICULTURAL EXPERIMENT STATION. I9II. 



chicken three zueeks old.* These figures are for the whole of 

 the hatching season of 1911, that is, from February i to June i. 

 They do not rejDresent the normal reproducing ability of the 

 stock because of the heavy handicap explained above. In spite 

 of this fact, however, these records can only be regarded as 

 indicating an excellent performance. 



Certainly these figures for hatching and rearing give no' sup- 

 port to the view that the constitutional vigor or vitality of the 

 Station Barred Plymouth Rock stock has been impaired by many 

 years of continued artificial incubation and rearing. When it 

 takes but three eggs or less to produce a chick three weeks old 

 the stock cannot be said to be in a condition of reduced vitality. 



4. It is plain that there is no substantial difference between 

 the females of the high fecundity lines and the females of the 

 low fecundity lines with respect to hatching records. What 

 small differences there are indicate that birds of the high fecun- 

 dity lines are on the whole somewhat surer reproducers than 

 those of the low fecundity lines. While the percentage of infer- 

 tile eggs is smaller in the low fecundity lines, on the other hand 

 the^percentage of fertile eggs hatched is also lower and a slight- 

 ly larger percentage of chicks died during the first three weeks 

 of their lives. Particular attention is called to this matter here 

 because it has been alleged by one critic that selection for 

 high egg production was inimical to reproductive capacity in 

 the domestic fowl. As a matter of fact, as the present figures 

 show, this is not at all the case. The criticism was based upon 

 a fact previously brought out ** that there is a negative correla- 

 tion between winter egg production and the hatching quality of 

 eggs in the subsequent breeding season. This, however, is 

 purely a physiological and not a genetic matter. High laying 

 during the winter months undoubtedly tends to bring about a 

 somewhat fatigued condition of the whole reproductive system 

 with the result that the eggs in the subsequent spring do not 

 hatch quite so well as under other circumstances. This, how- 

 ever, has nothing to do with the innate hereditary capacity of 

 these same birds in respect to fecundity. This fact is indeed so 



* As is well known three weeks covers nearly the entire chick mortality. 

 The subsequent death rate among chicks which at three weeks of age 

 are in full health and vigor is relatively insignificant. 



** Cf., Pearl and Surface, loc. cit. 



