INCONCLUSIVE CONCLUSIONS 505 



If the sex of the offspring is not determined by environmental 

 conditions, on what does it depend ? It may depend on a num- 

 ber of minute and variable factors, such as the relative ages of 

 the parents and the relative ages of the sex-cells when they unite 

 in fertilisation, or it may be " hereditary." It seems difficult, 

 at present, to decide which of these views should be adopted, 

 but, in any case, the facts point clearly to the conclusion that, 

 in man at least, the sex is fixed unalterably at or soon after 

 fertilisation. 



But what is meant by sex being " hereditary " ? It means 

 {a) that the particular sex-ratio now general has been long esta- 

 blished, and it is known that there has been an excess of male 

 births in England for at least two hundred years ; and {h) that 

 what results from any individual fertilised ovum — whether a 

 male or a female offspring — is determined by the compromise 

 effected between the ancestral contributions that constitute the 

 inheritance. 



