No. 485] 



THE DETERMIXA TIO.X OF Si:X 



305 



Strasburger (:00) made main- cxpcrimnits with (lid-emus j)l:ints- 

 growing them on various kinds of soil and imdcr various condi- 



tions, in the attempt to 



modify tlie 



sexual ratio, 



. Tiio followir 



resuhs with Melandrinm 



albnm may 1 



l)e cited as an 



example: 





lABLE 







Kind of i^oil 





Females 



/' ' 





410 



562 





Unfertilized garden soil 



235 



282 





Fertilized field soil 



384 



479 



124.4 



Unfertilized field soil 



254 



307 



120.8 



Sand 



321 



411 



128.0 



Totals 



1604 



2041 



Mean 127.2 



Thus sexual ratios for groups of plants grown under the most 

 diverse nutritive conditions did not differ greatly from the mean. 

 Strasburger concluded that an arbitrary determination of sex in 

 dioecious phanerogams has never been accomplished, and he is 

 inclined to apply this conclusion to all plants. 



Rauber (:00) studied statistically the distribution of sex in man. 

 He found everywhere an excess of male births, but this early excess 

 in the young was changed, because of the greater mortality of 

 the males,^ to an excess of females in later life, and particularly 

 in old age. He showed that the sexual ratio for Europe was 1000 

 female to 1060 male births, and that this mean ratio was fairly 

 constant in the different parts of Europe. Reasoning on the basis 

 that, if sex was determined by environment, the great diversity 

 of external conditions in tlie different parts of Europe should 

 cause a considerable difference in the sexual ratios for the differ- 

 ent countries, he concluded that sex is hereditary in man. 



x'Vccording to Rauber, there is uonnally an excess of female 

 births in horses, sheep and certain other donic.^tic animal-. 



Punnett (:04a) has made a statistical stndy of the disirihntion 



