Are Acquired Habits inlieritedf 287 



inheritance, a congenital instinct in the house martins of 

 to-day. Natural selection has no doubt been keeping up 

 the standard of organic efficiency and of average intelli- 

 gence, the weakly and foolish having been weeded out ; but 

 it has not been the efficient cause of the specialized instinct 1 

 of building beneath the eaves. Such would be the view of 

 those who accept the hereditary transmission of acquired 

 habits. 



Those who hold the other view would, I take it, begin 

 by questioning, or at least demanding satisfactory proof of, 

 the fact that the habit of building in this special manner 

 and place is a truly congenital instinctive activity. They 

 would remind us that the adaptive intelligence which 

 enabled the house martins of the past to adopt this method 

 of nidification is still operative. They would further 

 urge that the nestlrngsanTbrought up under the eaves, 

 and that there is ample opportunity for the formation 

 of an association between nests and eaves. They would 

 contend that there is nothing in the nest itself that 

 cannot fairly be interpreted as the direct outcome of the 

 conditions under which each particular nest is built, 

 nothing, that is to say, for which any congenital variations 

 of instinctive activities is required. Any congenital 

 tendency (at present quite unproven) which there might be, 

 they would attribute entirely to natural selection. In the 

 open country, far from rocky fastnesses, those martins in 

 which there was a congenital tendency to build beneath 

 the eaves, would bring up their broods and transmit this 

 tendency ; those in which this tendency was absent would 

 either go elsewhere or fail to bring up broods at all. 

 This would be their second line of defence in case the 

 habit be shown to have a truly instinctive basis. 



So far it has been my aim merely to bring out the 

 distinction between the rival theories of the manner in 



