64 DOMESTICATED ANIMALS AND PLANTS 
the reduction would proceed furthest, but, in general, such is 
not the case. 
For example, many more species of plants will grow together 
on poor land than on rich, and if fertilizer be applied to such a 
spot supporting a feeble growth of many species, their number 
will be at once reduced. 
The reason of it is that under generally hard conditions noth- 
ing succeeds well enough to institute a vigorous fight, but as 
soon as conditions are improved, as by the addition of fertilizer, 
then at once some species will succeed so well as to crowd others 
down and possibly out. This is one test of the natural fertility 
of lands, namely, the number of species found growing together 
upon it in a state of nature; and the same principle is employed 
by good farmers who make the land so rich that the crop will 
choke out the weeds.! 
Survival of the fittest. The result of natural selection is the 
survival of the fittest. This does not mean the best from any 
standpoint of ours, but it does mean the ones that fit best into 
all the conditions that determine the issue of the struggle? It 
would be the woodpecker with the longest and hardest bill, the 
wolf with the best scent and the highest speed, the bull with 
the sharpest horn and the strongest neck ; indeed, among savage 
animals it means the supremacy of the longest tooth and the 
sharpest claw. 
Among the hunted it means the horse with the fleetest foot 
and the greatest endurance. It means the deer or moose with 
1 This principle also explains the relative inaction of the desperately poor 
and distressed portion of the degenerate class. If they were better fed, they 
would be more aggressive and consequently more dangerous. So does natural 
selection work among humans as elsewhere. 
2 For example, a savage and a sage may be so situated that skillful running 
alone will save life. Then for that purpose running becomes the test of sur- 
vival, and the savage alone may be able to meet the test, in which case his is 
the best “ fit” with the conditions. Under most conditions, however, the sage 
would have the advantage. All this means that the best trained man is the 
one that is able to meet and fit into the greatest variety of conditions that are 
likely to come his way. 
