10 GEOGRAPHICAL DISTRIBUTION [CHAP. VII 



Letter 386 To J. D. Hooker. 



Down, Feb. 2ist [1870]. 



I read yesterday the notes on Round Island l which I 

 owe to you. Was there ever such an enigma? If, in the 

 course of a week or two, you can find time to let me hear 

 what you think, I should very much like to hear : or we 

 hope to be at Erasmus' on March 4th for a week. Would 

 there be any chance of your coming to luncheon then ? 

 What a case it is. Palms, screw-pines, four snakes not 

 one being in main island lizards, insects, and not one 

 land bird. But, above everything, such a proportion of 

 individual monocotyledons ! The conditions do not seem 

 very different from the Tuff Galapagos Island, but, as 

 far as I remember, very few monocotyledons there. Then, 

 again, the island seems to have been elevated. I wonder 

 much whether it stands out in the line of any oceanic 

 current, which does not so forcibly strike the main island ? 

 But why, oh, why should so many monocotyledons have come 

 there ? or why should they have survived there more than 

 on the main island, if once connected ? So, again, I cannot 

 conceive that four snakes should have become extinct in 

 Mauritius and survived on Round Island. For a moment 

 I thought that Mauritius might be the newer island, but the 

 enormous degradation which the outer ring of rocks has 

 undergone flatly contradicts this, and the marine remains 

 on the summit of Round Island indicate the island to be 

 comparatively new unless, indeed, they are fossil and extinct 

 marine remains. Do tell me what you think. There never 

 was such an enigma. I rather lean to separate immigration, 

 with, of course, subsequent modification ; some forms, of 



1 In Wallace's Island Life, p. 410, Round Island is described as an 

 islet " only about a mile across, and situated about fourteen miles 

 north-east of Mauritius." Wallace mentions a snake, a python belonging 

 to the peculiar and distinct genus Casarea, as found on Round Island, 

 and nowhere else in the world. The palm Latania Loddigesii is 

 quoted by Wallace as "confined to Round Island and two other adjacent 

 islets." See Baker's Flora of the Mauritius and the Seychelles. Mr. 

 Wallace says that, judging from the soundings, Round Island was 

 connected with Mauritius, and that when it was " first separated [it] 

 would have been both much larger and much nearer the main 

 island." 



