PEARL— SEX RATIO IN DOMESTIC FOWL. 



423 



These figures show that if we take all of the 22,791 chicks, on 

 which this table is based, into account together we get a mean sex 

 ratio of 49.45, or approximately one half of one per cent, fewer 

 males than females. This, however, cannot be regarded as the 

 normal sex ratio for the strains of poultry and the environmental 

 complex here dealt with, because (a) the table shows an obvious 

 influence of size of family on the sex ratio, a point to which we 

 shall return for detailed discussion later in the paper, and (b) fami- 

 lies under 10 cannot be considered as representative of the normal 

 fertility of the domestic fowl. The value for families of 10 and 

 over, namely i?^ ^48.58 ± .28 (944), is certainly to be regarded as 

 much nearer the true biological norm for the sex ratio of this group 

 of poultry under the environmental conditions prevailing at the 

 Maine Station. 



Taking this value as the normal one, how does it compare with 

 other values for other strains of poultry, and for other birds do- 

 mestic and wild? Unfortunately there are very few data available 

 for comparison. Curiously enough, this lack is most pronounced 

 where it would be least expected, — namely in the case of poultry. 

 Table VII. contains all the data, involving numbers large enough 

 to be statistically of any significance, with which the writer is ac- 



TABLE VII. 

 Sex Ratio Statistics for Various Birds. 



Bird, 



Pigeon . . . 

 Pigeon. . . 

 Canary . . 

 Canary . . 

 Fowl .... 

 Fowl .... 

 Fowl .... 



(f cf per 1,000 99 ■ 



Authority. 



1. 159 

 1,052 



770 

 3.533 



947 

 806 



944 



Cuenot^ 



Cole and Kirkpatrick^ 

 Heape ^ 

 Heape ^ 

 Darwin ' 

 Fields 



Pearl, this paper. Families 

 of 10 and over. 



4 Cuenot, L., Bulletin Sci. France et Belg., T. 32 (5th Ser., T. i), pp. 



462-535, 1899. 



s Cole, L. J., and Kirkpatrick, W. F., Rhode Island Agric. Expt. Stat. 

 Bulletin, 162, pp. 463-512. 1915. 



6 Heape, W., Proc. Cambridge Phil. Soc., Vol. XIV., pp. 201-205, 1907. 



'^ Darwin, C, " The Descent of Man," Vol. I. 



8 Field, G. W., Biol. Bulletin, Vol. II., pp. 360-361, 1901. 



