126 MAINE AGRICULTURAL EXPERIMENT ' STATION. I9II. 



result will be a steady and definite, if gradual, deterioration of 

 the stock in respect to vitality or constitutional vigor and pro- 

 ductiveness. 



Now since a time previous to the beginning of the selection 

 experiment at this Station in 1898 no chicken has ever been 

 hatched on the Experiment Station plant except in an incuba- 

 tor nor reared in any other way than in a brooder. That is 

 to say, the flock of hens on the Experiment Station plant in 

 191 1 represents the end link in an unbroken chain of more than 

 13 years (which here mean "generations") of continuous arti- 

 ficial incubation and artificial rearing. It is quite evident, I 

 think, that if these processes do bring about deterioration of 

 the stock in vitality and productive qualities such deterioration 

 ought by this time to be beginning at least to make itself ap- 

 parent. 



The possibility that such a deterioration in vitality and pro- 

 ductiveness due to continued artificial incubation and rearing 

 was the real reason why during the period of mass selection 

 from 1898 to 1907 there was no improvement in the average 

 egg production of the flock but instead a slight decrease cer- 

 tainly demands careful consideration. This interpretation of 

 the results has specially appealed to a number of poultrymen. 

 Thus Dryden * says (loc. cit. p. 382) : 'Tn the nine years breed- 

 ing work at the Maine Station artificial methods were used in 

 hatching and brooding the chicks, and while we are guessing 

 at the failure to secure high egg yield in this experiment I ven- 

 ture to guess the failure was due to a gradual lowering of vital- 

 ity in the stock. by artificial incubation." 



' The question then to be considered, in light of all the available 

 facts, is as to whether there was during the course of the experi- 

 ment in selection any lowering of vitality due to this cause, and 

 further whether this can be regarded as the explanation of the 

 failure of an increase in average egg production to appear dur- 

 ing the selection period. 



From the nature of the experimental work which it was 

 desired to do it was impossible practically to employ natural 

 methods of hatching and rearing when the writer took charge 



* Dryden, J. Artificial vs. Natural Incubation. Rpt. Am. Breeders' 

 Association. Vol. V. pp. 380-382, igoQ. 



