210 THE HISTORY OF SCIENCE 



aquatic enemies. The terrestrial species is confined to 

 the central part of the group ; it is smaller than the 

 aquatic species, and feeds on cactus, leaves of trees, 

 and berries. 



Fifteen new species of sea-fish were obtained, dis- 

 tributed in twelve genera. The archipelago, though 

 not rich in insects, afforded several new genera, each 

 island with its distinct kinds. The flora of the Gala- 

 pagos Islands proved equally distinctive. More than 

 half of the flowering plants are native, and the species 

 of the different islands show wonderful differences. 

 For example, of seventy-one species found on James 

 Island thirty-eight are confined to the archipelago 

 and thirty to this one island. 



In October the Beagle sailed west to Tahiti, New 

 Zealand, Australia, Keeling or Cocos Islands, Mau- 

 ritius, St. Helena, Ascension ; arrived at Bahia, Brazil, 

 August 1, 1836 ; and finally proceeded from Brazil 

 to England. Among his many observations, Darwin 

 noted the peculiar animals of Australia, the kanga- 

 roo-rat, and " several of the famous Ornithorhyri- 

 chus paradoxus" or duckbill. On the Keeling or 

 Cocos Islands the chief vegetable production is the 

 cocoanut. Here Darwin observed crabs of monstrous 

 size, with a structure which enabled them to open 

 the cocoanuts. They thus secured their food, and 

 accumulated "surprising quantities of the picked 

 fibres of the cocoanut husk, on which they rest as a 

 bed.'* 



In preparing his Journal for publication in the 

 autumn of 1836 the young naturalist saw how many 

 facts pointed to the common descent of species. He 

 thought that by collecting all facts that bore on the 



