TAYLOR : DOMINANCT IN NATURB. 
9 
This is, however, einiiiently uDtenable and inisleadinf]^, for it is now 
ahnost universiilly conceded that all existing faunas and floras merely 
exhibit a passing and temporary phase in the earth's history and are 
and always have been tiirougliout countless ages in process of con- 
tinuous although slow and gradual migration, this migration being 
always in a direction away from the evolutionary centre and due 
not only to increasing numbers but to tlie genesis of more highly 
endowed species, which eventually drive their progenitors or pre- 
decessors from their native regions, the dispossessed species en- 
countering in their retieat many diverse and enervating conditions 
of climate, etc., resulting in a loss of some of the initi.d energy or 
vitality engendered in their ancestors, by the invigorating conditions 
under which tliey were evolved, and, therefore, to speak of such weaker 
species diffusing into and occupying areas dominated by the more 
advanced and stronger life of Europe is to fail to appreciate the 
efficiency of the organic barrier they form. 
North-Central Europe is confessedly the metropolis of all the most 
advanced types of aniujal and plant life of the world and cannot be 
successfully and permanently occupied by the organisms of the weaker 
adjacent legions, all of which had probably been ages ago expelled 
therefrom ; there is, therefore, little or no interchange of life between 
the stronger and weaker countries, though the actuality of such 
mutual interchanges has been frequently affirmed. 
The various ancient species now isolated in the more remote and 
scattered districts of these islands are representative remnants of life 
now dominant in other and weaker countries and are to be regarded as 
the last lingering relics of a former general occupation and their 
presence must not be interpreted as indications of a former hypo- 
thetical invasion of isolated areas from Lusitanian, American or other 
primitive regions. 
The distribution and dispersal of species is a process governed by 
universal and immutable law, and not, as some aver, accomplished 
by chance, or by the scattering at random by wind or ocean currents 
of species and individuals, and although it cannot be denied that 
anemophilous and certain other plants may extend their range to 
regions where they did not formerly occur, if the wind or water-borne 
seeds alight on unoccupied ground, or on land occupied by species 
much inferior in their dominating power ; yet it cannot be too strongly 
emphasized that weak or primitive plants or animals cannot effect a 
})ermanent footing and extend their range on ground monopolized by 
the more modern and highly endowed species. 
Although the natural tendency in the dispersal of life is towards 
uniform diffusion, and comparable to the concentric rippling caused 
by throwing a stone into a pool of water, resulting in a series of waves, 
the later ones taking the places of those pieviously formed, and the 
first produced being the furthest removed from the source ; so in like 
manner the later evolved species or genera dispossess their predeces- 
sors, and the earliest evolved are the furthest removed from the area 
in which they arose. 
