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 1 , " 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 2 , " 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 3 , 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. a Ibid. pp. 210, 211. 



3 Independently suggested, on somewhat different lines, by Profs. J. Mark Baldwin, 

 Henry F. Osborn and the writer. 



