24 BIRDS' NESTS 



tools with which those nests are constructed. Dr 

 Wallace suggests that this may be due to the physical 

 structure of the builder ; but I believe the many and 

 wide differences in the structure of nests may be 

 saf&ly attributed to far more important and deeply 

 rooted influences. Instead, therefore, of viewing the 

 Swift's rude nest, or the Ring Dove's wicker cradle 

 as the inevitable results of imperfect natural appli- 

 ances, they should be considered as structures made 

 perfect for the transient purpose they serve, and com- 

 pletely in harmony with the requirements of their 

 builders. On the other hand, instead of regarding 

 the nest of the Chaffinch and the Wren merely as 

 structures the paragon of perfection and architec- 

 tural skill, the results of perfect natural tools, thay 

 should be looked upon as nests, the only object their 

 beauty and perfection serves being a utilitarian one. 

 A bird's beak and its legs and feet are the tools with 

 which its nest is made; perhaps we might also in- 

 clude the breast, for many species make considerable 

 use of that part of the body in working some of the 

 materials. Yet, as I hope shortly to demonstrate, 

 neither on the form, the length, nor any other peculi- 

 arity of these parts does the comparative beauty and 

 perfection of the nest depend. Now we all know that 

 the Wren has a finely-pointed bill and long legs. With 

 these tools she builds a well-made nest which seems 

 to owe its perfect form and well-woven walls to the 

 little creature's nest-building appliances. But how 



