144 TEE ZOOLOGIST. 



have aided in such differentiation and that the pairing-place 

 should ultimately expand into a " bower " would be a result 

 brought about by the high and gradually increasing sesthetic 

 faculties of the birds constructing it. One can understand, too, 

 that as the thalamum passed into a bower, and as the bower 

 became more and more elaborate and complicated, its original 

 purpose might be gradually obscured, superseded, and more or 

 less lost sight of. Such, indeed, has been the case with our own 

 houses and gardens, which in the manifold wants, tastes, and 

 pleasures that they now minister to, have become something very 

 different to their rude originals — beginning with the mere cave — 

 amongst primitive savages. There has, too, been the process of 

 differentiation as between the bedroom and sitting-room or bower. 

 What was the original cave but a sleeping place ? 



I believe that the key to the unlocking of many of the wonder- 

 chambers of bird doings is to be sought in the highly nervous 

 and excitable organization which birds, as a class, possess, and, 

 especially, in the extraordinary development of this during the 

 breeding and rearing time. This nervous sexual or parental 

 excitation produces all sorts of extravagant motions and antics 

 which are at first quite useless, but on the raw material of which 

 both natural and sexual selection have seized and are constantly 

 seizing. By these two powers they have been or are being 

 directed into various useful channels, such as nest-building, 

 ruses to decoy enemies from the young, displays of plumage by 

 one sex to the other, and so forth. On this view the fact of many 

 bird (or other) antics not being attributable to sexual selection 

 should not be used (as it has been used) to throw discredit on 

 that hypothesis. By what agency the raw material has been 

 shaped in any one case is a question of the evidence in and 

 relating to such case. And as the exercise of intelligence in all 

 these matters would be an advantage, intelligence, as I believe, 

 has, by the same means, through memory, been gradually worked 

 and woven into them, giving to some or all species a special 

 intelligence in some special directions, which, though much above 

 the general level of its capacity, yet reacts upon this and tends 

 to raise it. I believe, too, that, if closely watched, many actions 

 of birds which seem now to be altogether intelligent and purposive 

 (and, no doubt, are so to a very large extent) will be found to 

 betray traces of a nervous and non-purposive origin. 



