420 ORIGINATIVE FACTORS IN EVOLUTION: 



that the negress has 24, at least in some cases. Now in the 

 white man and woman the enumerations of Winiwarter and 

 others have usually been 47 and 48. It seems curiously 

 difficult to reach certainty in regard to this simple point, 

 but there is no harm in asking, as Dr. Gates does, whether 

 the white man may not have originated from a black race 

 by a " tetraploid mutation and its consequences ". 



The nuclear changes studied in GZnothera in their as- 

 sociation with particular mutations are not restricted to 

 changes in the number of chromosomes; they may concern 

 their shape, size, and structure. What has been gained is 

 a demonstration that in some cases the bodily peculiarities 

 of mutants are correlated with visible changes in germinal 

 organisation. 



Now one is quite aware that this is just telescoping-down 

 the Proteus of the full-grown organism into the germ-cell 

 phase of its being, and that a recognition of germinal dis- 

 turbances does not tell us what conditions them. As Professor 

 Bateson has often said, we find ourselves confronted with 

 the oppressive difficulty of cell-division and irregularities 

 in its procedure. Yet there is an enlightening gleam in the 

 proof that somatic mutations are correlated with antecedent 

 germinal disturbances, for we know that abnormal cell-divi- 

 sions occur in various conditions in Nature, and we have 

 already referred to the opportunities for re-arrangements 

 that occur in the early history and maturation of the germ- 

 cells. Is there any further light? 



We must remember that chromosomes are living units in 

 a complex environment, and just as Bacteria sometimes 

 change suddenly in their physiological properties, so chromo- 

 somes may vary in their stereochemic architecture or in 

 functional powers. Moreover, it is not fanciful to suppose 



