DEPARTMENT OF EXPERIMENTAL EVOLUTION. 135 



selection have been summarized. The summaries of the data indicate 

 that there is an effect of selection. The strains (1, 4, and 6) selected 

 to become more intergrade probably have not become more inter- 

 grade, but of the three strains (3, 5, and 8) selected to become more 

 nearly normal-female-producing, two have become markedly less 

 intergrade than they formerly were (in fact, almost exclusively normal- 

 female-producing) and markedly less intergrade than the three strains 

 selected for increasing the intergrade characters. One of the strains 

 (8) selected to become less intergrade has not made progress in the 

 desired direction during the past 16 generations (the only period for 

 which the data have been summarized), though it had apparently done 

 so during the 21 earlier generations of selection. A return selection 

 is rendered extremely desirable and is to be undertaken as soon as 

 the lines now being utilized are disposed of. 



SEX-RATIO IN MAN. 



Some years ago. Professor Raymond Pearl tested a view that has 

 had some scientific currency, that hybrid matings tend to produce an 

 excess of male offspring. He utilized for the purpose a record of the 

 sex of offspring of matings in Argentina between native-born stock 

 and those between immigrants from different countries. Dr. Little 

 has tried to secure more extensive material and has been making use 

 of the records of lying-in hospitals in the city of New York. A de- 

 tailed study has been made, with the assistance of Miss Beatrice W. 

 Johnson, of the records of the Sloane Maternity Hospital of New York 

 City. The purpose was to compare the sex-ratio in the progeny of 

 various types of racial matings. Matings in which both parents 

 were from European (Caucasian) races were chosen. For the purpose 

 of this study the term race is used in the sense of a biological center of 

 more or less inbreeding. Thus, generally speaking, a mating of two 

 Irish parents is a type of closer inbreeding than a mating in which one 

 parent is Irish and the other Italian. Then a comparison between 

 two such types of matings has been made. The races used were as 

 follows: English, Irish, Scotch, German, Austrian, Russian, Italian, 

 and Greek. These were tabulated in two main groups: (a) those 

 matings in which both parents came from the same race, and (6) 

 those in which the parents were from different races. While much 

 information still remains to be gathered from the data, that part which 

 concerns the ratio of the sexes among the offspring (including still- 

 births) has been tabulated, with the results shown in table 5. 



Several facts stand out as of general interest. Three of them re- 

 semble each other so closely as to suggest that a single explanation 

 may properly include them all. These are: (1) the excess of male 

 progeny found in the normal "pm-e" racial matings; (2) the signifi- 

 cantly greater excess of males found in offspring of the ''hybrid" 



