468 
THE GEOLOGIST. 
nature, but far more easily, from having incomparably longer time at her dis- 
posal. Nor do 1 believe that any great physical cliange, as of climate or of any 
iinusxial degree of isolation to check immigration, is actually necessary to pro- 
duce new and unoccupied places for natural selection to fill up by modifying 
and improving some of the varying inhabitants. Por as all the inhabitants of 
each country are struggling together with nicely balanced forces, extremely 
slight modifications in the structui-e and habits ot one inhaljitaut would often 
give it an advantage over others ; and still fiu'ther modifirations of the same 
kind woidd often still further increase the advantage. No coimtry can be 
named in which all the natural inhabitants are now so perfectly adapted to each 
other, and to the physical conditions under which they live that none of them 
could any how be improved ; for in all countries the natives have been so far 
conquered by naturalized productions, that they have allowed foreigners to take 
firm jrossession of the land. And as foreigners have thus everywhere beaten 
some of the natives, we may safely conclude that the natives might have been 
modified with some advantage, so as to have better resisted such intruders. 
As man can produce, and certainly has produced, a great result by his methodical 
and unconscious means of selection, what may not natvu'e effect ? Man can 
act only on external and visible characters; nature cares nothing for appearances, 
except in so far as they are useful to any being. She can act on every internal 
organ — on every shade of constitutional difference — on the whole machinery of 
life. Man selects only for his own good ; Nature only for that of the being 
which she tends. Every selected character is fully exercised by her : and the 
being placed under well-suited conditions of life. Man keeps the natives of 
many cHmates in the same country ; he seldom exercises each selected character 
in some peculiar and fitting mamier ; he feeds a long- and short-backed pigeon 
on the same food ; he does not exercise a long-backed, or a long-legged quad- 
ruped in any peculiar manner ; he exposes sheep with long- and short-wool to 
the same climate. He does not allow the most vigorous males to struggle for 
the females. He does not destroy aU inferior animals, but protects during each 
varying season, as far as lies in his power all his productions. He often begins 
his selection with some half -monstrous form; or at least by some modification 
prominent enough to catch his eye, or to be plain and useful to him. Under 
nature the slightest diiference of structure, or constitution, may well turn the 
nicely -balanced scale in the struggle for Ufe, and so be preserved. How fleeting 
are the wislies and efforts of man ! how short his time ! and, consequently, 
how poor his products wiU be compared with those accumulated by nature 
dui-ing whole geological periods ! Can we wonder, then, that nature's produc- 
tions should be far " truer" in character than man's productions — that they 
should be infinitely better adapted to the most complex conditions of life, and 
should plainly bear the stamp of far higher workmanship ? It may be meta- 
phorically said that natural selection is daily, hom-ly scrutinizing throughout the 
woi-ld evei-y variation, even the slightest ; rejecting that which is bad, preserving 
that which is good; silently and invisibly working whenever and wherever 
opportunity offers, at the improvement of each organic being in relation to its 
organic and inorganic conditions of life. We see nothing of these slow changes 
in progress until the hand of time has marked the lapse of ages, and then so 
imperfect is our view into long past geological ages, that we only see forms of 
life are now different from what they formerly were. * * * Slow though 
the process of selection may be, if feeble man can do much by his powers of 
artificial selection, I can see no Kmit to the amount of change, to the beauty 
and infinite complexity of the co-adaptations between all organic beings, one 
with another, and with their physical conditions of life, which may be effected 
in the long course of time by nature's power of selection." 
The evident modifications of primitive type-plans, which indisputedly we see 
