NATURAL SELECTION 224 
wishes and efforts of man! how short his time! and consequently how 
poor will be his results, compared with those accumulated by Nature 
during whole geological periods! Can we wonder, then, that Nature’s 
productions 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 metaphorically be said that natural selection is daily and 
hourly scrutinizing, throughout the world, the slightest variations; 
rejecting those that are bad, preserving and adding up all that are 
good; silently and insensibly working whenever and wherever oppor- 
tunity 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 see only that the forms of life are now different from what 
they formerly were. 
In order that any great amount of modification should be effected 
in a species, a variety when once formed must again, perhaps after a 
long interval of time, vary or present individual differences of the same 
favorable nature as before; and these must be again preserved, and 
so onwards step by step. Seeing that individual differences of the 
same kind perpetually recur, this can hardly be considered as an 
unwarrantable assumption. But whether it is true, we can judge only 
by seeing how far the hypothesis accords with and explains the general 
phenomena of nature. On the other hand, the ordinary belief that 
the amount of possible variation is a strictly limited quantity is like- 
wise a simple assumption. 
Although natural selection can act only through and for the good 
of each being, yet characters and structures, which we are apt to con- 
sider as of very trifling importance, may thus be acted on. When we 
see leaf-eating insects green, and bark-feeders mottled-gray; the 
alpine ptarmigan white in winter, the red-grouse the color of heather, 
we must believe that these tints are of service to these birds and 
insects in preserving them from danger. Grouse, if not destroyed at 
some period of their lives, would increase in countless numbers; they 
are known to suffer largely from birds of prey; and hawks are guided 
by eyesight to their prey—so much so, that on parts of the Continent 
persons are warned not to keep white pigeons, as being the most liable 
to destruction. Hence natural selection might be effective in giving 
