life, both of the individual and species. Necessarily so, seeing that,
for one thing, instincts can only arise and grow to perfection in order
to meet cases which commonly occur in the life of a species. The
instinct is not prophetic and does not meet rare or extraordinary
situations. Unless intelligence or some higher faculty comes in to
supplement or to take the place of instinctive action then the creature
must perish on account of the limitation of instinct. Again, the higher
and more complete the instinct the more perilous it is, seeing that its
efficiency depends on the absolutely perfect health and balance of all
the faculties and the entire organism. Thus, the higher instinctive
faculty and action of birds for the preservation of the species, that of
migration, is undoubtedly the most dangerous of all. It is so perfect
that by means of this faculty millions and myriads of birds of an
immense variety of species from cranes, swans, and geese down to minute
goldcrests and firecrests and the smallest feeble-winged-leaf warblers,
are able to inhabit and to distribute themselves evenly over all the
temperate and cold regions of the earth, and even nearer the pole: and
in all these regions they rear their young and spend several months each
year, where they would inevitably perish from cold and lack of food if
they stayed on to meet the winter. We can best realize the perfection of
this instinct when we consider that all these migrants, including the
young which have never hitherto strayed beyond the small area of their
home where every tree and bush and spring and rock is familiar to them,
rush suddenly away as if blown by a wind to unknown lands and continents
beyond the seas to a distance of from a thousand to six or seven
thousand miles; that after long months spent in those distant places,
which in turn have grown familiar to them, they return again to their
natal place, not in a direct but ofttimes by a devious route, now north,
now north-east, now east or west, keeping to the least perilous lines
and crossing the seas where they are narrowest. Thus, when the returning