■ 2 o 8 The Nahtralist in La Plata. 
for representation, meets the liglit'at the requisite 
angle, and that point alone should be shown in full 
brilliance of colour. A floAver j 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 
Avith pages ten or fifteen feet Avide by eighteen feet 
long, each one showing a cloud of humming-birds 
of one species flitting about a floAvery 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- 
Avfse sombre plumage, Avould 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 Dainvin thought, 
or are merely the outcome of a superabundant 
vitality, as Dr. A. D. Wallace so strongly maintains, 
is a question Avhich science has not yet answered 
satisfactorily. Idie 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 
