PARENTAL ALCOHOLISM AND THE PROGENY 251 



An adequate method of collating and digesting the data in 

 such a way as to make an answer to these questions possible 

 appears to be afforded by the 'poultry selection index' devised 

 by Pearl and Surface (27, p. 392) some years ago. This index 

 is described in this way: 



The formula which has been provisionally adopted in our work as 

 a fundamental poultry selection index is as follows : 



^ ^ (g + 6) 

 - c + d+ ; 

 The following scheme shows the meaning of the letters in the formula : 

 7i = general or fundamental poultry selection index for an individual 



bird. 

 a = percentage of this bird's fertile eggs which hatched. 

 h = percentage of eggs actually laid by this bird to the total number 

 it was possible for her to lay between February 1 and June 1 

 (i.e., the breeding season) of the year for which the index is 

 calculated. 

 c = percentage of this bird's eggs which were infertile. 

 d = percentage of chicks which died within three weeks from the 

 date of hatching. 



In the present connection, and probably generally, it is better 

 to designate this constant as the 'poidtry breeding index' rather 

 than 'selection' index. The values of the poultry breeding index 

 for the 1915 alcoholic matings are set forth in table 3, together 

 with the subsidiary values on which they are based. In the 

 case of matings 2105 and 2108 inclusive, in which the ether 

 females were involved, it will be recalled from table 2 -that these 

 birds were killed on April 15 by too long a stay in the tank. 

 In calculating the breeding index for these birds the factor b 

 in the formula for index has been taken as the percentage of 

 eggs actually laid by each bird to the total number it was possi- 

 ble for her to lay between February 1 and April 15. 



From this table it is evident that there is a good deal of varia- 

 tion in the breeding index in the different matings. The con- 

 stant ranges in value from 1.3 to 99.6. The highest value 

 tabled by Pearl and Surface for this index was 45.2, 



The relation between" total reproductive capacity as indi- 

 cated by the index, and the total germ dosage with alcohol is 

 shown graphically in figure 1. The total germ dosage index 



