466 EVOLUTION, GENETICS, AND EUGENICS 



individuals on a scale of 10. Ten represents very high ability, as 

 determined by the comparative amount of space and laudation given 

 to the individual in such standard works as Lippincott's Biographical 

 Dictionary. Five out of eight of Isabella's great-grandparents rank 

 very high. John the Great of Portugal, twice her great-grandfather, 

 has a grade of 10. John of Gault, twice her great-grandfather, has a 

 grade of 8, as does also John of Castile, while Henry III of Castile, one 

 of her grandparents, is designated the model king. Ferdinand I of 

 Aragon, the grandfather of Ferdinand, is a brother of this same 

 Henry III of Castile, and is also an exceedingly able king. Of the 

 children of Ferdinand and Isabella, most were mediocre or distinctly 

 inferior. Joanna was insane. In the next generation, however, appears 

 Charles V, whose reign marked the acme of Spain's greatness, partially 

 due to his own ability, partially due to the momentum of those move- 

 ments that were instituted by his illustrious grandparents. Charles V 

 married his own cousin, as did also John III. Children of these two 

 matings married, and Don Carlos, child of this latter marriage, was 

 madly depraved and cruel. 



"When insanity and brilliancy are found in the ancestry it seems 

 merely a matter of chance as to whether the determiners for greatness 

 will be thrown together in the union of sperm and egg or those for 

 insanity. We can predict with some certaintythat, in a large number 

 of offspring, ability will reappear and insanity will reappear, but just 

 what individual each will strike it is impossible to prophesy without 

 knowing much more definitely the nature of the germ plasm involved. 

 One may say that the convergence of a number of lines of descent from 

 great ancestors toward one individual makes it probable that he will 

 be exceptionally able. 



"This is nowhere better illustrated than in the family tree of 

 Frederick the Great of the Prussian house of Hohenzollern, as will be 

 seen from the chart on page 467. Of his great-grandparents, three 

 scale 10, one 9, one 8, two 7, and one 6. Not one is below mediocrity, 

 and the majority are of very high grade. Of his fourteen ancestors 

 back three generations, only one is distinctly inferior. Of his brothers 

 and sisters, four are distinctly great, three mediocre, and one inferior. 



"It is interesting to trace the effect of the mating of such splendid 

 stock with another brilliant line, that of the Swedish royal house. 

 Gustavus I, or Gustavus Vasa, is another instance of the brilliant 

 mutant, with some taint of neurosis. He married a gentle and tactful 

 princess; their son Charles TX was a very able man, although of their 



