216 The Naturalist in La Plata. 
Gould tried to obtain others, offering as much as 
fifty pounds for one; but no second specimen ever 
gladdened his eyes, nor was anything more heard 
of it until Stolamann refound it in the year 1880. 
The addition of many new species to the long 
list would, however, be a matter of small interest, 
unless fresh facts concerning their habits and 
structure were at the same time brought to light ; 
but we can scarcely expect that the as yet un- 
known species will supply any link connecting the 
Trochilidz with other existing families of birds. 
The eventual conclusion will perhaps be that this 
family has come down independently from an 
exceedingly remote past, and with scarcely any 
modification. While within certain very narrow 
limits humming-birds vary more than other families, 
outside of these limits they appear. relatively 
stationary; and, conversely, other birds exhibit 
least variability in the one direction in which 
humming-birds vary excessively. On account of a 
trivial difference in habit they have sometimes been 
separated in two sub-families: the Phaéthornithine, 
found in shady tropical forests; and the Trochiline, 
comprising humming-birds which inhabit open sunny 
places—and to this division they mostly belong. In 
both of these purely arbitrary groups, however, the 
aérial habits and manner of feeding poised in the 
air are identical, although the birds living in 
shady ferests, where flowers are scarce, obtain 
their food principally from the under surfaces of 
leaves. In their procreant habits the uniformity is 
also very greai. In all cases the nest is small, deep, 
cup-shaped, or conical, composed of soft felted mate- 
