28 A NATURALIST'S WANDERINGS 



finished, did I fully realise what a precious anti-corrosive in 

 these humid regions I had lost. 



The Birgus, though belonging to a water-living family, 

 spends' the greater part of its time on the land, and Professor 

 Semper* has discovered that, following on its change of habit, 

 a portion of the gill-cavities of this singular crustacean have 

 become modified into an organ for breathing air — " into a true 

 lung," in fact. 



Not less interesting than the marine, was the terrestrial life 

 of these lonely isles. Mr. Darwin's famous visit was made 

 about eleven years after their colonisation. More than half a 

 century more had elapsed till I landed there. In 1836 Mr. 

 Darwin gathered some twenty-two species of flowering plants. 

 On comparing the list (at the end of this Part) of the plants 

 collected or identified on the atoll by me with Professor Hens- 

 low's of those collected by Mr. Darwin, it will be observed that 

 considerable additions have been made to its flora. It is not 

 improbable, however, that a few of those not enumerated by 

 Professor Henslow may have been overlooked by Darwin during 

 the occupied days of the Beagle's short stay. Some are of more 

 recent introduction, and are due with little doubt to the 

 accidents of human inter-communication, while others have 

 been intentionally introduced. Direct intercourse has princi- 

 pally been with Java, Mauritius, and India, and occasionally 

 with Australia, by means of horse-laden vessels calling for 

 water. The greater part of the indigenous vegetation consists, 

 as Mr. Darwin has pointed out, of plants common to Australia 

 and Timor ; and it is certainly these we should most expect to 

 find here, as the ocean currents which wash the shores of the 

 atoll by running westward from Australian seas, and sweeping 

 round north-eastward in the Indian Ocean towards Sumatra 

 and Java, bring it nearer to Australia and the eastern part of 

 the Archipelago than to its geographically closer neighbours.. 

 Thus by slow degrees and after many a failure have the ocean 

 streams succeeded in clothing this lone speck with verdure. 



When first occupied ihe islands were covered abundantly 

 with iron-wood (Gordia) and Pemphis acidula, as well as cocoa 

 palms. Accidental fires, however, both on North Keeling 



* Cf. ' The Natural Oonciitions of Existence as they affect Animal Lifr,' by 

 Karl Semper. International Series ; p. 193. Kegan Paul & Co. 1881. 



