INTRODUCTION. XXVil 
the colours which adorn them ; but some species do not require such pro- 
tection, the birds being well able to guard them from any enemies by their 
own prowess. The law of imheritance explains this:—The Gulls have 
descended from a common ancestor—a form probably intermediate between 
a Gull and a Plover, which depended on the colour of its eggs for their 
safety ; and consequently we find a certain type of eggs peculiar to the 
whole group, of benefit to the majority of species, of little or no service 
to a few, but still retained by the law of inheritance. 
Those birds building open nests amongst the foliage of trees and shrubs, 
as a rule, lay eggs more or less of a green colour. The Crows in the top- 
most branches, the Thrushes in the lower shrubs, and many of the Warblers 
in the dense undergrowth may be cited as instances. Again, the Bullfinch 
and the Greenfinch lay bluish-white eggs, spotted with red, in open nests ; 
but these birds build in the darkest thickets and hedgerows and amongst 
evergreens. 
A word as to the marvellous variation and beautiful colours of the eggs 
of the Guillemot. The extraordinary amount of variation in the colour 
of these eggs appears to be a grave difficulty, and one which utterly refuses 
to conform to those laws that govern the tints with which so many birds’ 
eggs are adorned. It is one of those very few instances where Nature has 
seemingly run riot in her variations, in a similar manner to those which 
occur in domesticated animals; for once let the checks to variation be 
removed, and its ramifications are infinite and endless in a few generations. 
Why, we are apt to ask, do the Guillemot’s eggs vary so considerably ? 
Why are they allowed to present such diversity of colour whilst the eggs 
of most other birds are strictly confined to certain tints? We may attri- 
bute the vast variation in the colouring of their eggs to the comparatively 
easy conditions under which they are brought to maturity. The birds’ 
haunts are practically inaccessible ; they have few enemies of their eggs 
and young, and the variations which occur in their eggs are consequently 
of small moment. Each variety, according to the Guillemot’s present con- 
ditions of life, has no more favour than the other; but should the conditions 
of their existence change, should their eggs be exposed to some new danger, 
the variety best suited to those changed conditions would doubtless be most 
favoured—the others not so suitably coloured would, in the course of time, 
ultimately be weeded out by a rigorous selection, and the colours would 
most probably be confined to certain uniform protective tints. The colour 
of birds’ eggs is hereditary. A Guillemot that lays a green egg, always 
lays a green egg, and it will transmit. the faculty of laying a green egg to 
its offspring. This circumstance is not peculiar to the Guillemot, but is 
common to all birds; and the variation we see in every species is the 
produce of certain individuals and is transmitted to their young. Hence 
it is easy to imagine how thé Guillemot’s eggs would soon revert to a 
