2o8 The Naturalist in La Plata. 



for representation, meets tlie light at the requisite 

 angle, and that point alone should be shown in full 

 brilliance of colour. A flowery shrub is sometimes 

 seen surrounded by a cloud of humming-birds, all 

 of one species, and each, of course, in a different 

 position. If someone would draw such a scene 

 as that, showing a different detail of colour in each 

 bird, according to its position, then some idea of 

 the actual appearance of the bird might be given 

 to one who had never seen an example." 



It is hardly to be expected that anyone will carry 

 out the above suggestion, and produce a monograph 

 with pages ten or fifteen feet wide by eighteen feet 

 long, each one showing a cloud of humming-birds 

 of one species flitting about a flowery bush ; but 

 even in such a picture as that would be, the birds, 

 suspended on unlovely angular projections instead 

 of " hazy semicircles of indistinctness," and each 

 with an immovable fleck of brightness on the other- 

 wise sombre plumage, would be as unlike living 

 humming-birds as anything in the older mono- 

 graphs. 



Whether the glittering iridescent tints and 

 singular ornaments for which this family is famous 

 result from the cumulative process of conscious or 

 voluntary sexual selection, as Darwin thought, 

 or are merely the outcome of a superabundant 

 vitality, as Dr. A. R. "Wallace so strongly maintains, 

 is a question which science has not yet answered 

 satisfactorily. The tendency to or habit of varying 

 in the direction of rich colouring and beautiful or 

 fantastic ornament, might, for all we know to the 

 contrary, have descended to humming-birds from 



