FACTS OF INHERITANCE 139 



In this reduction, which means in the case of the 

 egg the absolute rejection of half of the chromo- 

 somes (which are carried off by the first polar 

 body and come to nothing), we see an opportunity 

 for permutations and combinations among the 

 items of the inheritance, e.g. for the dropping out 

 of a character altogether. 



Not less important is the visibly demonstrable 

 fact that sperm and ovum contribute the same 

 number of chromosomes (except in certain cases 

 where half of the spermatozoa have an extra 

 chromosome), and that, when the fertilised egg- 

 cell divides, each daughter-cell receives the normal 

 number of chromosomes, half of maternal origin 

 and half of paternal origin. This has been followed 

 for several divisions, so that, if the chromosomes 

 are inheritance-bearers, we have ocular demonstra- 

 tion of the truth of the prophetic statement which 

 Huxley made in 1878 : " It is conceivable, and 

 indeed probable, that every part of the adult 

 contains molecules derived both from the male 

 and from the female parent ; and that, regarded 

 as a mass of molecules, the entire organism may 

 be compared to a web of which the warp is 

 derived from the female and the woof from the 

 male." 



STATISTICAL STUDY : FILIAL KEGRESSION. 

 Darwin's illustrious cousin, Sir Francis Galton, 

 has been the leader in the statistical study of 

 inheritance. He has shown the value of collecting 

 statistics as to the resemblances and differences 

 in successive generations, e.g. as regards stature, 

 colour of eyes, and intellectual ability, and he 

 has reached several general inductions which 

 express the inherent orderliness obtaining even 



