428 Mental Factors in Evolution 
but also, to some extent, the modifications are inherited. He there- 
fore held that some instincts (the greater number) are due to natural 
selection but that others (less numerous) are due, or partly due, to 
the inheritance of acquired habits. The latter involve Lamarckian 
inheritance, which of late years has been the centre of so much 
controversy. It is noteworthy however that Darwin laid especial 
emphasis on the fact that many of the most typical and also the most 
complex instincts—those of neuter insects—do not admit of such an 
interpretation. “I am surprised,” he says’, “that no one has hitherto 
advanced this demonstrative case of neuter insects, against the well- 
known doctrine of inherited habit, as advanced by Lamarck.” None 
the less Darwin admitted this doctrine as supplementary to that 
which was more distinctively his own—for example in the case of 
the instincts of domesticated animals. Still, even in such cases, “it 
may be doubted,” he says’, “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, 
@ more recently suggested hypothesis, that of organic selection®, 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 inter- 
pretation. 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) Varia- 
1 Origin of Species (6th edit.), p. 233. 2 Ibid. pp. 210, 211. 
3 Independently suggested, on somewhat different lines, by Profs. J. Mark Baldwin, 
Henry F. Osborn and the writer. ; 
