314 GEOGRAPHICAL DISTRIBUTION 
here to go much into details! The question, often mooted, of 
recognizing a distinct Circumpolar Region need not be discussed, 
for it has not become practical; and whatever may be the case 
as regards other Classes, it seems almost impossible for the orni- 
thologist reasonably to refuse recognition, as regards Birds, of the 
siz Geographical Regions—New-Zealand, Australian, Neotropical, 
Holarctic, Ethiopian, and Indian, brigading, if he so please, the 
first three as Notogxva, and the last three as Arctogxa, but always 
bearing in mind that the differences between each of the component 
parts of the former, and especially the differences between New 
Zealand and all the rest of the world, are not only more striking, 
but far more essential than those presented by the component parts 
of the latter. 
It is admitted by nearly all naturalists that the study of the 
extinct organisms of any country leads the investigator to a proper 
appreciation of its existing Flora or Fauna; while on the other hand 
a due consideration of the plants or animals which predominate 
within its bounds cannot fail to throw more or less light on the 
changes it has in the course of ages undergone. ‘That is to say, 
the Distribution of living creatures in Time is so much connected 
with their Distribution in Space that the one can hardly be con- 
sidered without the other. Granting this as a general truth, it 
must yet be acknowledged as a special fact already foreshadowed 
when treating of Foss, Birps, that we at present have in them 
but scanty means of arriving at precise results which would justify 
bold generalization as regards the Distribution of the Class. Com- 
pared with other Vertebrates, fossil remains of Birds are exceedingly 
scarce, and have been until lately little investigated. However 
suggestive be the discovery in France of somewhat early remains 
of Birds allied to those which we at present only know as living 
denizens of tropical countries, and the recognition of far later 
remains of species identical with those that now flourish in arctic 
lands, these facts merely corroborate what is from other sources 
within the cognoscence of every geologist—the vicissitudes, namely, 
to which that part of Europe has been subjected. Even the former 
existence of RATIT# in England and other countries where they are 
not now found only proves that they were once not confined to their 
present limits, and possibly pervaded the greatest part of the earth. 
Almost the same is to be said of every other case, and perhaps in 
the whole range of zoology there is no Class from the fossil 
remains of which we learn less as regards the physical history of 
our planet than we do from the Birds. We therefore have to turn 
to the other side of the question and try to find whether the 
1 Prof. Heilprin has stated (loc. primo cit.) the probability that “ portions 
of California, Texas, and Florida will have to be relegated to the Neotropical 
realm.” Mexico would naturally follow ; but hereon more will be said hereafter. 
