Still, even in such cases, "it may be doubted," he says (Ibid. pages
210, 211.), "whether any one would have thought of training a dog to
point, had not some one dog naturally shown a tendency in this line... so
that habit and some degree of selection have probably concurred in
civilising by inheritance our dogs." But in the interpretation of the
instincts of domesticated animals, a more recently suggested hypothesis,
that of organic selection (Independently suggested, on somewhat
different lines, by Profs. J. Mark Baldwin, Henry F. Osborn and the
writer.), may be helpful. According to this hypothesis any intelligent
modification of behaviour which is subject to selection is probably
coincident in direction with an inherited tendency to behave in this
fashion. Hence in such behaviour there are two factors: (1) an
incipient variation in the line of such behaviour, and (2) an acquired
modification by which the behaviour is carried further along the same
line. Under natural selection those organisms in which the two factors
cooperate are likely to survive. Under artificial selection they are
deliberately chosen out from among the rest.

Organic selection has been termed a compromise between the more strictly
Darwinian and the Lamarckian principles of interpretation. But it is not
in any sense a compromise. The principle of interpretation of that which
is instinctive and hereditary is wholly Darwinian. It is true that some
of the facts of observation relied upon by Lamarckians are introduced.
For Lamarckians however the modifications which are admittedly factors
in survival, are regarded as the parents of inherited variations; for
believers in organic selection they are only the foster parents or
nurses. It is because organic selection is the direct outcome of and a
natural extension of Darwin's cardinal thesis that some reference to it
here is justifiable. The matter may be put with the utmost brevity as
follows. (1) Variations (V) occur, some of which are in the direction
of increased adaptation (+), others in the direction of decreased
adaptation (-). (2) Acquired modifications (M) also occur. Some of these
are in the direction of increased accommodation to circumstances (+),
while others are in the direction of diminished accommodation (-). Four
major combinations are

(a) + V with + M,
(b) + V with - M,
(c) - V with + M,
(d) - V with - M.

Of these (d) must inevitably be eliminated while (a)