CHAPTER X 



THE DETERMINATION OF SEX 

 1. Speculations, Ancient and Modern 



From the earliest times the desirabihty of con- 

 trolhng the sex of an unborn child, in particular 

 instances at least, has seemed very great. Likewise 

 the wish to be able to predetermine sex among do- 

 mesticated animals has made breeders quick to grasp 

 at every clue that promised success. 



There has been no want of speculations concerning 

 the determination of sex. J. Arthur Thomson, 

 who with Professor Geddes wrote "The Evolution 

 of Sex" in 1889, says : "The number of speculations 

 as to the nature of sex has been well-nigh doubled 

 since Dreylincourt, in the eighteenth century, 

 brought together 262 'groundless hypotheses' and 

 since Blumenbach caustically remarked that nothing 

 was more certain than that Dreylincourt's own theory 

 formed the 263rd. Subsequent investigators have 

 long ago added Blumenbach's theory of 'Bildungs- 

 trieb' or formative impulse, to the list." It maybe 

 added in passing that the hypothesis of the deter- 

 minative action of external factors upon developing 

 germ-cells which Geddes and Thomson elaborated 

 in the book just referred to, has, in its turn, accord- 

 ing to most biologists, joined the long roll. 



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