Birds of New Zealand. 219 
are Jiving 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 he 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 f 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, 
