Chap. X. STATE OF DEVELOPMENT. 337 



more recent forms must, on my theory, be higher than 

 the more ancient; for each new species is formed by 

 having had some advantage in the struggle for life 

 over other and preceding forms. If under a nearly 

 similar climate, the eocene inhabitants of one quarter 

 of the world were put into competition with the exist- 

 ing inhabitants of the same or some other quarter, 

 the eocene fauna or flora would certainly be beaten 

 and exterminated; as would a secondary fauna by an 

 eocene, and a palaeozoic fauna by a secondary fauna. 

 I do not doubt that this process of improvement has 

 affected in a marked and sensible manner the organ- 

 isation of the more recent and victorious forms of life, 

 in comparison with the ancient and beaten forms ; but 

 I can see no way of testing this sort of progress. 

 Crustaceans, for instance, not the highest in their own 

 class, may have beaten the highest molluscs. From 

 the extraordinary manner in which European pro- 

 ductions have recently spread over New Zealand, and 

 have seized on places which must have been previously 

 occupied, we may believe, if all the animals and plants 

 of Great Britain were set free in New Zealand, that in 

 the course of time a multitude of British forms would 

 become thoroughly naturalized there, and would exter- 

 minate many of the natives. On the other hand, 

 from what we see now occurring in New Zealand, and 

 from hardly a single inhabitant of the southern hemi- 

 sphere having become wild in any part of Europe, 

 we may doubt, if all the productions of New Zealand 

 were set free in Great Britain, whether any consider- 

 able number would be enabled to seize on places now 

 occupied by our native plants and animals. Under tins 

 point of view, the productions of Great Britain may be 

 said to be higher than those of New Zealand. Yet 

 the most skilful naturalist from an examination of the 



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