112 H. D. GOODALE AND GRACE MACMULLEN 



birds appear where none are expected. Moreover, Pearl's data 

 shows that 15.5 per cent of the Fi offspring from Cornish males 

 by Barred Plymouth Rock females lay more than 30 eggs, the 

 average excess production being 15.7 eggs or more than 50 per cent. 

 Now, the average winter production of these over-30 birds is al- 

 most .exactly the same (viz., 45.7 eggs) as that (viz., 46.2 eggs) 

 of the over-30 birds produced by Barred Plymouth Rock males 

 on Cornish females. It should be observed further that in most 

 cases the mean winter egg production of the over-30 group, in 

 cases involving the use either of Fi or pure Barred Plymouth 

 Rock males is also low, ranging from 35 to 57.2 eggs, the average 

 being 45.9. WTiile it is not feasible to pursue the analysis 

 further, because of the form in which the data is presented, yet 

 in view of the facts presented above, it is not hard to believe 

 that the results of these crossing experiments do not necessarily 

 involve sex linkage. 



THE BEARING OF MODIFICATIONS IN MANAGEMENT ON THE 



RESULTS 



When these experiments were started, it was with the intention 

 that the methods of management (i.e., the environment) to the 

 smallest detail should remain constant throughout the work. 

 Unfortunately, however, it soon developed that something was 

 radically wrong with the method of rearing the chicks, which 

 made changes here imperative. Later, results of the experi- 

 ments themselves made certain changes in time of housing the 

 pullets necessary. The various changes made are given in 

 appendix 1. 



Of the various changes there is only one, viz., a change in 

 method of rearing the chicks, that appears capable of affecting 

 the results to an appreciable degree, though it does so in two 

 ways. First, this change now gives us with certainty normal 

 adults to place in the laying houses. Second, it makes possible 

 the maintenance of the laying flocks in a state of freedom from 

 infect ous disease, particularly roup. Roup, althougn very 

 capricious in making its appearance, is favored by certain envi- 

 ronmental conditions, expecially the weather. Moreover, the 



