I’AUNISTIC SIGNIFICANCE OF EURASIAN TRACT. 
387 
The organisms of Europe, especially of Xortli Central Europe, being 
the most advanced in development, show this superiority in the most 
marked degree, and as may be e.xpected from their stronger yet more 
adai)table character and conseiiuent greater power of successfnl 
dispersal there are few peculiar species, and these consist chiefly 
of archaic and weaker types, which have not yet been eliminated, 
but are being gradually isolated or otherwise driven to the confines of 
the region before becoming finally extinct. 
This pre-eminence of its organic life may be partially consequent 
upon the diversity of its surfiice and the genial, yet bracing, climate 
it enjoys, free from the great extremes of heat and cold characterizing 
Siberia, Central Asia and even Eastern Europe, characters due to its 
permeation by the sea, and to the prevalence of genial westerl}" winds 
bringing moisture and warmth from an ocean whose temperature is 
modified by the gulf stream. 
The invigorating climate and variety of terrestrial conditions, com- 
bined with the complex nature of the organic environment, tends to 
confer a marked degree of adaptability on the species living therein, 
while the greater bionomic uniformity characterizing other divisions 
of the globe leads to a more exact adaptation with the special 
environment and favours high specialization, with consequent decrease 
or loss of adaptability to conditions other than those with which 
their variation is correlated, so that without prejudging the position 
of the chief centre of active evolution during former arrangements of 
land and water, we are led by these and other considerations and 
under present conditions to regard the Xorth Central European region 
as the birth-place of the chief types of life at present occupying the 
terrestrial portions of the globe; and, as progress is dependent not 
merely upon the nature of the physical but more essentially upon 
that of the organic environment, it is only by association with and 
competition amongst the strongest and most advanced races that the 
highest excellence or development can arise, so that we must still look 
to the Xorth Central European region for the continued evolution of 
the most adaptable and dominating forms of life, which the excessive 
severity of the life struggle will inevitably evolve. 
As although tropical climes conduce to the development of species 
of large size, brilliant colouration and a wondrous variety of ornamenta- 
tion, yet, probably partially owing to the weakness of their organic 
environment, they chiefly differentiate externally or specifically, by 
