258 THE 'ORIGIN OF SPECIES.' [i860. 



conquering those of lesser ; of course the Indian forms would 

 have a greater difficulty in seizing on the cool parts of Aus- 

 tralia. I demur to your remarks (page 1), as not " conceiving 

 anything in soil, climate, or vegetation of India," which could 

 stop the introduction of Australian plants. Towards the close 

 of the essay (page civ), you have admirable remarks on our 

 profound ignorance of the cause of possible naturalisation 

 or introduction ; I would answer p. 1, by a later page, viz. 

 p. civ. 



Your contrast of the south-west and south-east corners is 

 one of the most wonderful cases I ever heard of. . . . You 

 show the case with wonderful force. Your discussion on 

 mixed invaders of the south-east corner (and of New Zealand) 

 is as curious and intricate a problem as of the races of men in 

 Britain. Your remark on a mixed invading Flora keeping 

 down or destroying an original Flora, which was richer in 

 number of species, strikes me as eminently new and important. 

 I am not sure whether to me the discussion on the New Zea- 

 land Flora is not even more instructive. I cannot too much 

 admire both. But it will require a long time to suck in all 

 the facts. Your case of the largest Australian orders having 

 none, or very few, species in New Zealand, is truly mar- 

 vellous. Anyhow, you have now demonstrated (together 

 with no mammals in New Zealand) (bitter sneer No. 3), that 

 New Zealand has never been continuously, or even nearly 

 continuously, united by land to Australia ! ! At p. lxxxix, 

 is the only sentence (on this subject) in the whole essay at 

 which I am much inclined to quarrel, viz. that no theory 

 of trans-oceanic migration can explain, &c. &c. Now I 

 maintain against all the world, that no man knows anything 

 about the trans-oceanic power of migration. You do not 

 know whether or not the absent orders have seeds which 

 are killed by sea-water, like almost all Leguminosse, and 

 like another order which I forget. Birds do not migrate 



