212 THE ORIGIN OF SPECIES [pt. ii 



we shall endeavour to show, the same reply is valid in the case 

 of mutation. To expect to see the formation of a new species, 

 i.e. the survival of a mutation, in the short time since man began 

 to observe such matters, is rather sanguine than reasonable, and 

 especially in the north, where the adjustment of plant associ- 

 ations to the environment is probably very perfect, and where 

 consequently the establishment of a new form is correspondingly 

 difficult. Lord Rayleigh has estimated the period since the 

 Eocene alone, which covers but a portion of that occupied in 

 the evolution of the higher plants, at 30,000,000 years. But if 

 we suppose one mutation in 50 years to survive, we should get 

 the whole of the existing 160,000 species of flowering plants in 

 8,000,000 years, which is only 26 per cent, of that time. And 

 this mutation, be it remembered, may appear upon any small 

 spot anywhere in the world, most of which is not under sufficiently 

 close observation for us to be able to say whether or not any of 

 the many species that are confined to very minute areas has 

 arisen within the history of human record. If Tribidus ala- 

 cranensis (p. 152), or one of the other two Alacran species, has, 

 as is possible, arisen in the last 50 years, then there is no need 

 for any more species to arise for 50 (perhaps 150) years to come, 

 to keep up nature's average rate of evolution. 



When one considers how difficult it is for seed to get a chance 

 of germinating, growing, and surviving upon any given spot, 

 well covered, as most spots are, with a dense association of plants 

 that have already pro\'ed their suitability to the locality and its 

 conditions, it is clear that a new form must have the most com- 

 plete suitability at its birth to the local conditions, to get any 

 foothold. Not only so, but it must suit those conditions as they 

 will be modified by its OAvn appearance and addition to the 

 association of plants already there. Clearly, therefore, to talk 

 about advantage as having guided its evolution is to go some- 

 what beyond the warranty afforded by any of the facts as yet 

 at our disposal. 



Man can, and does, easily propagate a noA'elty^ by clearing 

 the ground of rivals, but in nature this will rarely happen. It 

 viay be that the very common presence of young species upon 

 islands and upon mountains is due to the fact that these places. 



1 "We have no reason to suppose that we have violated nature's laws in 

 producing a new variety of wheat — we may have only anticipated them; 

 nor is its constitution impaired because it cannot, unaided, perpetuate its 

 race; it is in as sound and unbroken health and vigour during its life as. 

 any wild variety is " (55 6, p. ix). 



