208 THE HISTORY OF SCIENCE 



dogs." A native boy, when asked by a traveler why 

 they do this, had answered, " Doggies catch otters, 

 old women no." In such hard conditions what are the 

 characteristics that would determine the survival of 

 individual or tribe ? One might be tempted to lay 

 almost exclusive emphasis on physical strength, but 

 Darwin was too wise ultimately to answer thus the 

 question that for six or seven years was forming in 

 his accurate and discriminating mind. 



On its way west in the Pacific the Beagle spent 

 a month at the Galapagos Archipelago, which lies 

 under the equator five or six hundred miles from the 

 mainland. " Most of the organic productions are ab- 

 original creations, found nowhere else ; there is even 

 a difference between the inhabitants of the different 

 islands ; yet all show a marked relationship with 

 those of America." Why should the plants and ani- 

 mals of the islands resemble those of the mainland, 

 or the inhabitants of one island differ from those of 

 a neighboring island ? Darwin had always held that 

 species were created immutable, and that it was im- 

 possible for one species to give rise to another. 



In the Galapagos Archipelago he found only one 

 species of terrestrial mammal, a new species of mouse, 

 and that only on the most easterly island of the group. 

 On the South American continent there were at least 

 forty species of mice, those east of the Andes being 

 distinct from those on the west coast. Of land-birds 

 he obtained twenty-six kinds, twenty-five of which 

 were to be found nowhere else. Among these, a hawk 

 seemed in structure intermediate between the buzzard 

 and polyborus, as though it had been modified and 

 induced to take over the functions of the South Ameri- 



