POULTRY NOTe;S — 1909. 



97 



Table 8. 



Shoiuing the Sex Ratio and Mortality Records of All Pure Bred 



Chicks Hatched from Pullet Eggs. Season of ipop. 





Number of 



different 



matings. 



Tojal chicks. 



Chicks died. 



Percentage 

 mortality. 



Mating. 



d 



? 



cf 



? 



d" 



? 



Barred Plymouth Rock cf and 5 . . 

 Cornish Indian Game cf and ? — 



Ill 

 12 



664 

 59 



698 

 76 



278 

 26 



238 

 29 



43 

 44 



34 

 38 



From these tables the following points are to be noted : 



1. In both hybrid matings a few more males than females 

 were produced. The differences, however, are so small as to 

 be insignificant. Practically an equal absolute number of males 

 and females were produced in the hybrid matings. In the pure 

 matings on the other hand there is a distinct and significant pre- 

 ponderance of females in both matings. 



2. It appears then to be the case that there is a tendency 

 shown in the 1971 chicks here under consideration for relatively 

 iTiore males to be produced in hybrid than in pure matings. 

 This result is in accord with a suggestion made by Davenport* 

 in the following words (p. 97) : "There is a widely held and 

 frequently expressed opinion that hybrids show an excessive 

 proportion of males." No support was given to this sugges- 

 tion by Davenport's own published statistics. His general con- 

 clusion was that, "The exceptions to the law of equality of sexes 

 in hybrid ofifspring are .... individual and not of general 

 significance." It was subsequently shown* that there is an 

 excess of males produced when certain human stocks are cross 

 bred as compared with the same stocks bred pure. 



The real test of whether the present poultry statistics defi- 

 nitely bear out the same conclusion must come from an exami- 

 nation of the probable errors of the sex ratios involved. Taking 

 the sex ratio as the percentage of males in the total number of 

 offspring we have the usual expression for the probable error of 

 a proportion 



*Davenport, C. B. Inheritance in Poultry. Carnegie Institution of 

 Washington, Pbl. No. 52, 1906. 



*Pearl, Maud D. and R. On the Relation of Race Crossing 10 the 

 Sex Ratio. Biol. Bulletin, Vol. 15, No. 4, pp. 194-205. 1908. 



