Notes on Foregoing Chapter 139 



species for generations together. The instinct will even 

 thus remain a very wonderful one, but it is not at all in- 

 consistent with the theory put forward by Professor 

 Hering and myself. 



Returning to the idea of psychical mechanism, he 

 admits that "it is itself so obscure that we can hardly 

 form any idea concerning it,"^ and then goes on to claim 

 for it that it explains a great many other things. This 

 must have been the passage which Mr. Sully had in view 

 when he very justly wrote that Von Hartmann " dog- 

 matically closes the field of physical inquiry, and takes 

 refuge in a phantom which explains everything, simply 

 because it is itself incapable of explanation." 



According to Von Hartmann^ the unpractised animal 

 manifests its instinct as perfectly as the practised. This 

 is not the case. The young animal exhibits marvellous 

 proficiency, but it gains by experience.^' I have watched 

 sparrows, which I can hardly doubt to be young ones, 

 spend a whole month in trying to build their nest, and 

 give it up in the end as hopeless. I have watched three 

 such cases this spring in a tree not twenty feet from my 

 own window and on a level with my eye, so that I have 

 been able to see what was going on at all hours of the 

 day. In each case the nest was made well and rapidly 

 up to a certain point, and then got top-heavy and tumbled 

 over, so that little was left on the tree : it was recon- 

 structed and reconstructed over and over again, always 

 with the same result, till at last in all three cases the birds 

 gave up in despair. I believe the older and stronger birds 

 secure the fixed and best sites, driving the younger birds 

 to the trees, and that the art of building nests in trees is 

 dying out among house-sparrows. 



^ Page 100 of this vol. ' Pp. io6, 107 of this vol. 



