CHAPTER XIII 



HEREDITY AND SEX 



§ I. Relations between Sex and Inheritance. 



§ 2. The Determination of Sex. 



§ 3. Different Ways of Attacking the Problem. 



§ 4. Classification of the Theories. 



§ 5. First Theory : Environment Affects Offspring. 



§ 6. Second Theory : Fertilisation is Decisive. 



§ 7. Third Theory : Two Kinds of Germ-cells. 



§ 8. Fourth Theory : Maleness and Femaleness are Mende- 



lian Characters. 



§ 9. Fifth Theory : Nurtural Influences Operate on the 



Germ-cells through the Parents. 



§ 10. Another Way of Looking at the Facts. 



§ 11. Conclusion. 



§ 1. Relations between Sex and Inheritance 



The main question here is : What determines sex ? but there are 

 some accessory questions. 



(a) Whatever " maleness " and " femaleness " may imply 

 in final analysis, there seems no doubt that a single germ-cell 

 may contain the potentiality of them both, and of all the mascu- 

 line and feminine characters as well. The drone-bee has a 

 mother, but no father, and many other instances are known 

 of unfertilised eggs developing into males, whose quality of 

 maleness and masculine characters are handed on through their 

 daughters to their grandsons. 



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