Birds of Neio Zealand. 219 



are living in America, these countries had also been united 

 with Australia. 



Speaking from a general point of view, I wish to add that 

 the attempts to trace the geographical relations of a fauna 

 and flora of a country can easily be exaggerated, and thus 

 a theory be ridden to death which otherwise would be very 

 useful. 



Moreover an unfortunate country, such as New Zealand, 

 of which a good number of the species of its fauna and flora 

 show great resemblance to other species from distant coun- 

 tries, has to be dipped down and brought up again a great 

 many times in order to establish connexions in various di- 

 rections, so that a bird or fish, a shell, insect, or centipede 

 might cross from the one to the other, moreover, without al- 

 lowing any other species from the same country to pass. 



Besides, the geological record of these islands at present at 

 our disposal does not warrant us to assume such repeated 

 changes in the level of the land. 



Cannot the explanation of such close specific resemblance 

 be found, in many instances at least, in the adoption of more 

 simple natural causes, such as the transport by icebergs, or 

 on floating islands, by birds, &c., of which Sir Charles Lyell, 

 in his great work, the ' Principles of Geology,' gives many 

 striking instances ? 



However, where the theory of land-connexion is not admis- 

 sible, and where also others, which have hitherto been applied, 

 fail, might we not assume that similar climatic and other phy- 

 sical conditions could produce similar specific characters under 

 the great law of evolution ? 



It is a most difficult problem to say what constitutes a 

 species ; and therefore might it not be safer to believe, until 

 the impossibility of such an hypothesis has been demonstrated 

 satisfactorily, that there exists a similitude as well as an iden- 

 tity of species under certain given conditions ? 



In one word, might we not throw out the conjecture that 

 in two more or less distant countries, which never were di- 

 rectly united, some forms of organic life can and do exist 

 which show what to us appears identical specific characters. 



