246 THE REIGN OF LAW. 



A similar principle of variation applies in other 

 genera, where the amount of difference is greater. 

 For example, one of the most singular and beauti- 

 ful of all the tribe is comprised within the genus 

 Lophornis, or the "Coquettes." The principle of 

 ornament in this genus is, that the different species 

 are all provided both with brilliant crests, and 

 with frills or tippets on the neck. The feathers 

 of these parts are generally of one colour, ending 

 in spots or spangles of another ; the spangles be- 

 ing generally of metallic lustre. There seems to 

 be a rule of inverse proportion between the two 

 kinds of ornament. The species which have the 

 neck plumes longest have the shortest crests, and 

 vice versa. In the shape and structure of all 

 essential organs there is hardly any difference 

 between the species. 



One very curious example of variety for the 

 sake of ornament may be mentioned in connexion 

 with this wonderful family of Birds. It is a law — 

 in the sense of an observed order of facts — regu- 

 lating the ornament of Humming Birds, that where 

 white is introduced into the colouring of the tail 

 feathers, it is not applied to the central feathers, 



