SEX-RATIO OF THE DEER-MOUSE. 151 



paper of Pearl and Pearl, though not referred to by these authors. 



Little (1919) has reported upon a smaller number of offspring 

 of " pure " and " hybrid " stocks, born at the Sloane Maternity 

 Hospital in New York City. The matings considered were those 

 within or between the following " races " : English, Irish, Scotch, 

 Italian, Russian, Greek, Austrian and German. Of the births of 

 "pure" stock, there were 5,753, and these gave a sex ratio of 

 106.27 1.81. Of the "hybrid" births there were 1,305, giving 

 a sex ratio of 121.56 4.49. The difference between these ratios 

 is a trifle over three times its probable error. In each case still- 

 births were included. It is of interest to note that the proportion 

 of stillbirths among the " hybrid " matings was considerably 

 lower than among the " pure." 



If the foregoing figures represent an actual biological differ- 

 ence between the two groups under consideration, the magnitude 

 of this difference is surprising. For each of the " pure " races 

 under consideration is, of course, not a race at all, biologically 

 speaking, but is itself a hybrid mixture. The basis employed in 

 these records was obviouslly nationality, not ethnic stock. 



In a later paper (1920) Little has divided his material into 

 " European pure," " European hybrid," ' LTnited States white," 

 " British West Indian colored," and " United States colored." 

 In general, the significance of Little's findings is greatly dimin- 

 ished if the probable errors are computed according to the for- 

 mula which has been employed in the present paper. Thus 

 computed, these are about double the errors given by Little. But 

 at least three of this author'-s differences remain of probable sig- 

 nificance, viz. : those between European pure ( 104.54) and Euro- 

 pean hybrid (122.86), between European pure (104.54) and 

 U. S. white (118.33), and between U. S. white (118.33) and 

 U. S. colored (96.12). It is of considerable interest that there is 

 no significant difference between European hybrid and United 

 States white. "This shows," as Little remarks, "that in the 

 data studied, the United States white ratio is essentially that of 

 a hybrid race," i.e., an even more hybrid one than the European 



" races.' 



