B i:pr OD UCTION. 485 



more boys are born in the country than in the city, and in poor than in pros- 

 perous families; the relative number of boys is said to vary even with the 

 price of food. It is contended, moreover, and with some statistical support. 

 that in the human race an epidemic or a war, either of which affects adversely 

 the well-being of the people, is followed by a relative increase of male births. 

 Statistics indicate also that the proportion of females is high in warm climates, 

 that of males high in cold climates. Maupas 1 found that sex in the rotifer. 

 Uydatina senta, could be controlled by altering the temperature of the medium 

 surrounding the egg-laying females. In various experiments at a tempera- 

 ture of 26°-28° C. 81-100 per cent, of the eggs gave rise to males, the resl 

 to females; at 14°-15° C. only 5-24 per cent, were male.-, the much larger 

 majority females. Nussbaum 2 has brought Ma upas's facts into harmony 

 with the facts regarding nutrition by showing that the higher temperature 

 carries with it a higher birth-rate and more rapid development, hence a 

 greater need of food and relative lack of it for the individual ; the result is 

 poor nutrition and the production of an excess of males over females. It is 

 claimed, further, that ethnic intermixture causes a decrease in the relative 

 number of males born. This is strongly supported by a statistical study by 

 Ripley 3 of the two races inhabiting Belgium, the Walloons, of the same 

 origin as the Kelts in France, and the Flemish of German stock. Where 

 these races are purest, the number of boys born to 1000 girls is 106 1 : along 

 the region where the two races come into contact, however, the number may 

 fall as low as 1043. 



The above considerations are highly interesting and suggestive, but they 

 have not yet been brought under general laws sufficiently to make their bear- 

 ing upon the main problem wholly clear. It is probable that numerous 

 factors are of influence in the determination of sex. 4 The general deduction 

 from all the facts seems justified that unfavorable nutritive conditions sur- 

 rounding the parents tend to the production of males, favorable conditions 

 to the production of females. The experimental results indicate, moreover, 

 that the conditions surrounding the parents or the developing embryo are 

 largely responsible for the resulting sex. Watase" regards the embryo as 

 neutral as regards sex from the time of fertilization up to a certain stage in 

 its development ; external conditions act as a stimulus to the sexless proto- 

 plasm, and the resulting response is a development in the direction of either 

 maleness or femaleness according to the nature of the stimulus. I low largely 

 and in what manner this may be true of the human species is wholly unknown. 

 Diising 6 urges that the various factors determining sex have arisen through 

 natural selection ; they are conducive to the continuance of the species, and 



1 K. Maupas: Complex nnrfus </<■ i'unitlt'mie des sciences, Paris, 1891, cziii. 

 'Nussbaum: Archivfiir mikroskopische Anatomic, 1897, \li\- 8. 227. 



3 W. X. Ripley : Quarterly Publications of the Imerican Statistical Association, March, L896, v, 



4 For a critical review of the various theories Bee I. ( ohn: Die willkiirliche Bestimtnung des 

 Geschlechts, 2d ed., Wiirzburg, 1898. 



5 S. Watase: Journal of Morphology, 1892, vi. 

 6 Dusing : Loc. cit. 



