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the face of an exuberant life, the ideally-armed robber must be 
satisfied with the off-fall of that life.”—(ftp. 6gg-yoo.) 
“ We see in our forests the societies formed by the young nut- 
catchers (Sitta cæsia), together with titmouses, chaffinches, wrens, 
tree-creepers, or some woodpeckers. In Spain the swallow is met 
with in company with kestrels, flycatchers, and even pigeons. In 
the far West the young horned larks live in large societies, together 
with another lark (Sprague’s), the skylark, the Savannah sparrow, and 
several species of buntings and longspurs. In fact it would be much 
easier to describe the species which live isolated than to simply name 
those species which join the autumnal societies of young birds, 
not for hunting or nesting purposes, but simply to enjoy life in society 
and to spend their time in plays and sports, after having given a few 
hours every day to find their daily food.”—(ft. yoi.) 
“ The quagga zebra . . . lives on excellent terms not only with 
ostriches but also with gazelles, several species of antelopes, and 
gnus—i.e., it lives together with ruminants feeding on the same 
grass as itself.”—(ft. yoy—note.) 
As the result of this co-operation it will sometimes 
happen that the best and fittest to live will perish in 
the act of defending the flock or herd to which they 
belong. But however this may be, it is quite clear that 
co-operation will prevent the sole survival of the fittest. 
The advocate of Natural Selection argues consistently 
with his theory that the improvement of the race is 
secured by the severity of the struggle between individuals 
of the same species. Weismann puts the case with 
admirable clearness. 
“ In order that any part of the body of an individual of any 
species may be kept at the maximum degree of development, it is 
necessary that all individuals possessing it in a less perfect form must 
be prevented from propagation—they must succumb in the struggle 
for existence. I will illustrate this by a special instance. In species 
which, like the birds of prey, depend for food upon the acuteness 
of their vision, all individuals with relatively weak eyesight must 
be exterminated, because they will fail in the competition for food. 
Such birds will perish before they have reproduced themselves, 
and their imperfect vision is not further transmitted. In this way 
the keen eyesight of birds of prey is kept up to its maximum.”— 
(Weismann. Essays, ft. agi.)