Uniformity of the work. 103 



and difference in the position of the nests. But 

 when we have discounted all these differences, there 

 remains a permanence of type to the work of In- 

 stinct in each species, almost equal to the perma- 

 nence of structure, size, color and other character- 

 istics that mark the species. So that we may fair- 

 ly say that the uniformity of Instinct in the work 

 of building, approaches the uniformity of physical 

 function in giving character to the animal. 



We have here then two very distinct statements 

 to make that seem borne out by careful observa- 

 tion. 



First, — That in the same species there is in 

 general great uniformity in all the elements of 

 building, as to materials, form, skilful work and posi- 

 tion. And, 



Second, — That birds so nearly allied as to be- 

 long to the same family, and even the same genus, 

 build in such diverse methods that their nests have 

 little or nothing in common, except that they are 

 nests. 



If we start with the assumption that each fami- 

 ly of birds came from one ancestor, it is perplexing 

 to understand how the slight differences of struc- 

 ture which mark the distinction between many spe- 

 cies, should be accompanied by such change of In- 

 stinct that there should be such great diversity in 

 building among birds of nearly allied species inhab- 

 iting the same district ; and yet such great uni- 

 formity and permanence of method among birds of 

 the same species. 



That the Baltimore Oriole should always hang 



