472, READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
three other children one was insane and two weak. The children of 
Charles IX were both remarkably able. The daughter Catherine 
becomes the mother of a later succession of kings. Her son Charles X 
and his son Charles XI were rather mediocre; but Charles XI, with 
this fine stock behind him, married Ulrica Eleanor (7), granddaughter 
of Christian IV of Denmark, the most brilliant of all Danish sovereigns, 
and Charles XII, their son, is pronounced by Voltaire the most 
remarkable man who ever existed. Charles XII had no children: 
the succession passed to his sister’s son, Adolph Frederick of Holstein- 
Gottorp, who married Louisa Ulrica, sister of Frederick the Great 
of Prussia. The result of this union of two great lines of hereditary 
ability was Gustavus III, a fit successor of Gustavus Vasa, Gustavus 
Adolphus, and Charles XII; he was “‘a prodigy of talents,” statesman, 
poet, dramatist. 
