CHAPTER I 



THE GENETIC THEORY OF 

 SEX-DETERMINATION 



Sex (L. seco, to cut), the distinction between male and female, the 

 property by which an individual is male or female. Sexuality, the 

 quality of being distinguished by sex. 



From the ver^^ beginning of human existence a difference 

 between the two contrasted types we know as male and 

 female respectively must have been recognized. Within 

 every individual the force of sexuality has operated to focus 

 thought upon matters sexual and to yield an intense aware- 

 ness of the sexually contrasted form. It can safely be assumed 

 that this observed difference in mankind and in the animals 

 man domesticated has at all times intrigued the human mind 

 and provoked speculation concerning its significance and 

 causation. Every individual displays the property of sexu- 

 ality and by his own experience knows of it. Speculation con- 

 cerning it has never been restricted to students of biology; 

 any man can claim to be his own authority. 



The observations that required an explanation were but 

 few to begin with. Maleness and femaleness were attributes 

 which were exercised in the sexual relationship. The sexual 

 union of male and female resulted in reproduction, in the 

 production of offspring among whom males and females 

 appeared in more or less equal numbers. In this production 

 by a male and a female of males and females there was to be 

 observed an orderliness and a precision which suggested that 

 some relatively simple mechanism was involved. 



Hypotheses concerning the way in which and the time 

 during the life history of the individual at which sex is 

 determined have been plentiful. For the most part they 

 were elaborated at a time when little or nothing was known 

 of the anatomy and physiology of the cell, of cell division, of 

 gametogenesis and of fertilization, or they were constructed 

 by such as were unaware of, or chose to disregard, what was 



I 



