of the Arctic and the Antarctic Faunas. 307 
OTHER VIEWS. 
This is perhaps the fittest place to discuss some of the 
other views which have a bearing on the question before us. 
A few investigators have admitted that it is necessary to 
assume a climate of tropical warmth in our latitudes to 
explain the Early Tertiary fauna; some of these, however, 
regard it as a local phenomenon, while others call in the aid 
of cosmic changes on a large scale. 
There is on the whole earth no other spot where all the 
factors which make for the amelioration of the climate and 
the warming of the surface-water are combined in anything 
like the same degree as on the Western and North-western 
coasts of Europe; it seems impossible to find conditions 
better fitted to bring about this result than those now pre- 
vailing ; so that in general this objection is hardly entitled to 
serious consideration. 
Other investigators incline to the view that the earth's 
axis has so altered its position either within the earth itself 
or in relation to the earth’s orbit that the climatic zones of 
earlier geological times were quite differently arranged, and 
may have shifted periodically over the earth’s surface. But 
astronomers refuse to admit the possibility of variation on 
such a scale, and geology and paleontology offer no evidence 
of it. Moreover, from the paleontological records of the 
Tertiary period it can be proved that there is no grounl for 
such an assumption, at least in regard to that period, with 
which we are alone concerned. 
We are now in a position to see that there is no argument 
of any weight against regarding the Karly Tertiary fauna as 
one of tropical habit. We have further seen that a climato- 
logical consideration of the problem excludes the theory that 
the fauna wasa localone. Geological-paleeontological inquiry 
yields the same result, inasmuch as the Karly ‘Tertiary faunas 
of tropical habit have been demonstrated from the most 
different parts of the earth, even from the southern hemi- 
sphere. We have accordingly to assume that in those times 
a climate of tropical warmth, with a fauna of tropical cha. 
racter, extended over the greater portion of the temperate 
zones. 
ORIGIN OF ZONALLY-DISPOSED F’auNAs. 
Now that we have seen that the climatolozical considera- 
tion of the Early Tertiary by reference to its faunistic 
materials is a scientifically justified standpoint, we have every 
ground for maintaining this standpoint with regard to the 
