48 THE NEXT GENERATION 



animals of the same general kinds were alive in all three 

 continents during the same era of the world's history. 



2. The theory which explains this is that in early times 

 there was land connection between Siberia and North America, 

 and that the joining place was where Bering's Strait now 

 separates the two continents. 



It is supposed that in those days this land connection was a 

 well-traveled road, across which animals of every sort and size 

 came as immigrants from the Old World to the New. " It 

 seems most probable," writes Darwin, " that the North Ameri- 

 can elephants, mastodons, horses, and the hollow-horned rumi- 

 nants migrated on land since submerged near Behring's Straits, 

 from Siberia into North America, and thence on land since 

 submerged in the West Indies, into South America, where 

 for a time they mingled with the forms characteristic of that 

 southern continent, and have since become extinct." 



From first to last, Darwin was searching for facts which 

 might connect one set of living creatures with all others. He 

 wished, if possible, to relate the life of the past even its 

 monsters to the life of the present. More than this, he 

 wished to relate the life of the present to the life of the fu- 

 ture. He hoped to find laws which would make it easier to 

 understand why there are such countless varieties of living 

 creatures on the earth to-day, and what their exact relation 

 to each other is. In other words, the reason why Darwin 

 gathered facts was because he was determined to find out as 

 much as possible about the progress of life on the earth from 

 generation to generation, through the ages of the past. 



This was the burden of his ambition, and facts were pil- 

 ing up as the Beagle continued its voyage to the Galapagos 

 Islands. 



