omary area of association and that of
reproduction must perforce widen. The question then arises: How will the
young that have no experience find their way to regions wherein they can
endure? The forces which may have been organised to subserve the end in
view are three: (1) Acquired experience, (2) tradition, (3) the
gregarious instinct. The pioneer that carries the range a little further
forward starts from a base where it has associated with companions and
found food plentiful; and when the impulse to live in society again
asserts itself, it not only repeats its former experience but hands on
the habit thus acquired to those of the next generation that happen to
accompany it. Granting, however, that by successive increments in the
distance traversed, traditional guidance may in time accomplish much, it
cannot account for all the known facts, it cannot at any rate explain
the fact that in some cases the inexperienced offspring finds its way to
the food area without guidance. Something, therefore, _is_ inherited.
And my suggestion is this: That the gregarious instinct, the ancient
origin of which we can infer from its manifestation in so many and
diverse forms of life, supplies the material upon which evolution works;
that variations of the initial impulse, at first slight and not in
themselves of selection value, in so far as they coincide in direction
with modifications of procedure due to experience or tradition, are
preserved; and that, in the process of time, they are so accumulated as
to form a specific congenital endowment determining a definite mode of
behaviour.

FOOTNOTES:

[1] June 1915, R. M. Barrington.

[2] _Dictionary of Birds_, p. 556.

[3] _Social Psychology._

[4] _Manual of Psychology._

[5] _Ibis_, April 1918.

[6] _Zoologist_, 1912, p. 327.

INDEX

Acquired experience, 300

Adjustments, transitory, of distribution, 275

Alarm notes, 119

Arrival, advantages and disadvantages of late, 33-44

Assemblies in winter, 262, 263

Assembly grounds, 173

Attainment of reproduction, 171

Barrington, R. M., on the sex of migrants, 25

Battle between two male Cuckoos, 82

---- between two Moor-Hens, 86, 92, 93, 94

---- ---- Pied Wagtails, 86

---- ---- Raven and Buzzard, 217

---- ---- Raven and Peregrine, 216
law of, 13,19

Behaviour routine, 262

---- sexual, 3

Bickerings, 96

Birthplace, return to, 43, 50