TIVO KIAWS OF OVA AND SPERMS 497 



ovum a bias towards the production of a female. On the latter 

 hypothesis we may perhaps find parallel phenomena in ants and 

 bees, where the unfertilised ova produce only males. For an 

 account of E. B. Wilson's exceedingly interesting observations 

 on Protenor helfragi, where ova fertilised by a spermatozoon with 

 an accessory chromosome develop into females, while those 

 fertilised by a spermatozoon without the accessory chromosome 

 become males, see Lock (1907), p. 253, where a Mendelian 

 interpretation of the facts is attempted. 



On our view, the difference between a gamete which produces 

 a male and another which produces a female is what we can only 

 vaguely call a difference in " physiological gearing," and it may 

 well be that the presence or absence of an extra chromosome is 

 one of the factors determining which " gear " is to find expression. 



Maturation. — It has been repeatedly suggested that in the 

 divisions which occur before the ova and the spermatozoa are 

 mature, divisions in which there is a reduction of the number of 

 chromosomes to half the number found in the body-cells, there 

 may be a definition of the sex-tendencies of the germ-cells. 

 But there does not seem to be the slightest warrant for connecting 

 the maturation-divisions with sex-determination — e.g. for sup- 

 posing that the egg becomes more purely female (the phrase 

 is rather an absurdity) or more liable to develop into a female 

 because it gives off two polar bodies. A parthenogenetic ovum 

 of the honey bee forms two polar bodies and yet develops into 

 a drone. We are not aware of a single fact which warrants 

 the suggestion that a maternal gamete becomes, by its matura- 

 tion divisions, more likely to produce a female organism. But 

 it is conceivable that if there are two kinds of ova and two 

 kinds of spermatozoa, with tendencies in each of the kinds 

 towards female-development or towards male-development, the 

 divisions associated with maturation may sharpen or blunt the 

 point of these tendencies. It is conceivable that a young ovum 

 with a cytoplasmic bias towards female-production may, in the 



