Part III.] OR POISONED BY VEGETABLE GROWTH? 
171 
the wave. And he has always, as species died out, 
and probably continues, even at this moment, to 
originate single stocks of new plants and animals, 
which radiate from where their Creator first lo¬ 
cates them as far round as his natural barriers will 
allow them. Lyell, in expounding these opinions, 
writes: — “In almost every district, especially if 
it be mountainous, there are a variety of species 
the limits of whose habitations are conterminous, 
some being unable to proceed further without 
encountering too much heat, others too much 
cold. Individuals which are thus on the borders 
of the regions proper to their respective species 
are like the outposts of hostile armies, ready to 
profit by every slight change of circumstances in 
their favour, and to advance upon the ground 
occupied by their neighbours and opponents. 
The proximity of distinct climates produced by 
the inequalities of the earth’s surface, bring 
species possessing very different constitutions 
into such immediate contact that their naturalisa¬ 
tions are very speedy whenever opportunities of 
advancing present themselves.” Now, these op¬ 
ponents , these outposts of hostile armies , “ possess¬ 
ing very different constitutions ,” and natives of 
distinct stations , might, from their perpetual pro¬ 
pinquity, be called by physiologists “ social 
plants;” as those of the same station are called 
