Multiple Origins 303 



the agency of birds; and when in explanation of the Scandinavian 

 elements in the Spitsbergen flora he had to choose between a former 

 land connection and the agency of birds, he preferred the bird 1 ." 



Darwin objected to "continental extensions" on geological grounds, 

 but he also objected to Lyell that they do not " account for all the 

 phenomena of distribution on islands 2 ," such for example as the 

 absence of Acacias and Banksias in New Zealand. He agreed 

 with De Candolle that " it is poor work putting together the merely 

 possible means of distribution." But he also agreed with him that 

 they were the only practicable door of escape from multiple origins. 

 If they would not work then "every one who believes in single 

 centres will have to admit continental extensions 3 ," and that he 

 regarded as a mere counsel of despair: — "to make continents, as 

 easily as a cook does pancakes 4 ." 



The question of multiple origins however presented itself in auother 

 shape where the solution was much more difficult. The problem, as 

 stated by Darwin, is this : — "The identity of many plants and animals, 

 on mountain-summits, separated from each other by hundreds of 

 miles of lowlands... without the apparent possibility of their having 

 migrated from one point to the other." He continues, " even as long 

 ago as 1747, such facts led Gmelin to conclude that the same species 

 must have been independently created at several distinct points; 

 and we might have remained in this same belief, had not Agassiz 

 and others called vivid attention to the Glacial period, which aflbrds 

 ...a simple explanation of the facts 5 ." 



The " simple explanation " was substantially given by E. Forbes 

 in 1846. It is scarcely too much to say that it belongs to the same 

 class of fertile and far-reaching ideas as "natural selection" itself. 

 It is an extraordinary instance, if one were wanted at all, of 

 Darwin's magnanimity and intense modesty that though he had 

 arrived at the theory himself, he acquiesced in Forbes receiving the 

 well-merited credit. " I have never," he says, " of course alluded 

 in print to my having independently worked out this view." But 

 he would have been more than human if he had not added : — " I was 

 forestalled in... one important point, which my vanity has always 

 made me regret ." 



Darwin, however, by applying the theory to trans-tropical 

 migration, went far beyond Forbes. The first enunciation to this is 

 apparently contained in a letter to Asa Gray in 1858. The whole is 

 too long to quote, but the pith is contained in one paragraph. "There 

 is a considerable body of geological evidence that during the Glacial 



1 Guppy, op. cit. 11. pp. 511, 512. - Life and Letters, n. p. 77. 



8 Ibid. ii. p. 82. * Ibid. n. p. 74. 



8 Origin of Species (6th ed.) p. 330. 6 Life and Letters, i. p. 88. 



