INTRODUCTION. | Xxix” 
throat’s nest is open and more or less exposed, and its eggs are dark green 
and protective in colour. 
One of the best examples coming into the present group that I know of 
is to be found in the Grass- Warbler (Cisticola cursitans). This bird builds 
a purse-shaped nest amongst the grass, in which the eggs are hidden from 
view; and these eggs exhibit several very distinct types—white or blue 
spotted with rufous, and sometimes unspotted blue or white. Another 
instance may be found in the Australian genus Chthonicola, i which the 
nest is domed and the eggs are red or chocolate in colour. 
What do these facts teach us? I think that their explanation is to be 
found in the fact that these domed nests have only comparatively recently 
been adopted by these species, and the eggs have not yet lost their colour. 
These coloured eggs show a changed mode of nesting. Their colour remains 
unchanged, or alters very slightly; and we know many other contrivances are 
retained long after their direct use has passed away, because they are not 
in any way injurious to the welfare of the species, yet they have always a 
tendency to die out; in the case of eggs this, I think, is shown in such 
instances as Cisticola, in which we so often find a colourless or plain type. 
We may rest assured that these ‘colours have not been acquired since the 
nest has been covered; they are a previous development, most probably 
destined in time to pass completely away if the present conditions under 
which the eggs are brought to maturity remain unchanged for any length 
of time. 
From a study of all these interesting facts we learn that birds’ eggs ex- 
hibit such great diversity of colour for other and far more important ends 
than that of mere beauty; and their varied tints must be viewed (with all 
other beauty of colour in nature) as an object by means of which great 
ends are attained. A few words should now be given to 
Generic types of eggs, and what they teach.—The true relationship 
of birds is often demonstrated by a study of their eggs. The family like- 
ness of birds, which extends through an entire natural group, is stamped 
indelibly on their eggs. Thus the experienced oologist, guided by their pecu- 
liar characteristics, is able to separate at a glance the eggs of the Shrikes, 
the Crows, the Snipes, the Birds of Prey, or those of any other large natural 
group of birds. ‘This is almost as apparent in shape as in colour. Snipe’s 
and Plover’s eggs are extremely pyriform; Kingfisher’s and Roller’s are 
round ; Pigeon’s, Goatsucker’s, and Sand-Grouse’s are oval; Grebe’s are 
pointed at each end. We find these characters constant in each group 
respectively. Take, for instance, the great family of the Ducks (Anatide), 
numbering nearly two hundred species distributed throughout the world. 
All their eggs possess certain characteristics which enable us readily to 
identify them. The same remarks apply to the Sandpipers (Scolopacidz) 
