EVOLUTION: OF INSTINCTIVE BEHAVIOUR 113 
without doing much to determine, survival. In any case these 
little instinctive traits, if they are so trivial as to seem of small 
value from the biological point of view, appear to be too 
unimportant to have been intelligently acquired as habits. 
Let us now consider one or two cases of instinctive behaviour 
which would fall under Romanes’s category of instincts of 
blended origin partly due to natural selection, partly to the 
inheritance of acquired habit. It is the custom of the house 
martin to build beneath the eaves. Forsaking the ancestral 
rocky haunts, it has been led to utilize the houses that 
man has built. This has all the appearance of being due 
to an intelligent modification of the ancestral instinet ; but 
how far the modification has become through heredity a 
congenital variation, we do not know. The intelligence 
which is said to have enabled the martin of the past to adopt 
this method of nidification is still operative. The nestlings 
brought up under the eaves would have opportunities for 
acquiring experience which might lead them to build under 
similar circumstances. Nest and eaves would be associated in 
the conscious situation. Nor would the effects of natural 
selection be necessarily excluded. One may suppose that in 
the open country, far from rock-shelters, those martins in 
which there was a congenital tendency to build in house- 
shelters would bring up their broods and transmit this 
tendency ; while those in which it was absent would either go 
elsewhere or fail to bring up broods at all. In the absence 
of fuller knowledge as to the truly instinctive nature of the 
behaviour, and as to its mode of genesis, we are in large 
degree at the mercy of conjecture. But in any case the in- 
cidence of elimination is not necessarily excluded, and there 
are, therefore, no graunds for denying that natural selection 
has been a co-operating factor in the evolution of the instinc- 
tive behaviour, if such it be. 
It is well known that the lapwing will apparently simulate 
the actions of a wounded bird, with the object, as it seems, of 
drawing intruders away from her nest. And such tactics are 
not restricted to this bird, nor even to one or two species. 
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