188 THE PRINCIPLES OF HEREDITY 



empires is past. There remains for them only temporary 

 conquest in a few malarious parts of the world in which 

 European nations cannot flourish and supplant the natives. 

 Spain and Portugal lost their opportunity when they turned 

 from the temperate regions and chose the tropics. France 

 lost her opportunity on the heights of Abraham. Germany 

 is more than a century too late in the start. Russia can 

 conquer only hardy aliens, who will multiply under her rule 

 and ultimately assert their supremacy. 



313. In times now far remote in the history of civilized 

 peoples, the sword was the principal means for digging deep 

 the foundations of permanent empires. Its place was taken 

 by a more efficient instrument. A migrating race, armed 

 with a new and deadly disease and with high powers of 

 resisting it, possesses a terrible weapon of offence. But now 

 disease has spread over the whole world and so is losing its 

 power of building empires. The long era of the great 

 migrations of the human race, of the great conquests, is 

 closing fast. 



