30 THE MEANING OF EVOLUTION 
similar beach marks on the sheer western face of the 
Andes, and found them without difficulty, confirming 
his idea of the recent rise of this end of the Andean 
chain. 
The Beagle continued its voyage up the western 
coast of South America until it reached Peru. Once 
more the abundance of tropical life is under Darwin’s 
eyes, but now it is the life of an entirely different 
section. The dry climate of Peru furnished him with 
an environment distinctly unlike that of the moist Bra- 
zilian forest. He collects now with avidity, gather- 
ing especially insects and birds. Then the ship turned 
its prow westward across the Pacific, only to stop five 
hundred miles out at the Galapagos Islands. This 
little group he studied intensely, collecting large num- 
bers of insects and birds. He had not worked over 
his collection long before he realized that each island 
in the group had peculiarities which marked its ani- 
mals from those of any other island. Whenever two 
islands were close together in the group the differ- 
ences in their fauna were found to be comparatively 
slight. If, however, he examined the animals from 
two islands lying at opposite ends of the group, the 
differences were always considerably greater. There 
was, however, a strong general resemblance among 
them all and a distant though not so strong resem- 
blance to the corresponding animals of the Peruvian 
