BIRDS' NESTS AND EGGS 371 



the Terns show more affinity to the true Plovers ; and this 

 may probably be accounted for by the nidification of each 

 group resembling most closely that to which the eggs are 

 allied in general appearance. The Game Birds are also 

 another instance. So far as I know, the eggs of these birds 

 never have any underlying markings — all the colour is on the 

 surface ; ^ and this is one great reason why the aberrant 

 Hemipodes should be excluded from this group of birds, for 

 their eggs possess both characters of markings, and therefore 

 show the bird's affinity to the Eails, the Plovers, and the 

 Bustards. It is also very remarkable how the eggs of some 

 birds resemble those of the species belonging to very distantly 

 related groups, where the conditions of nidification are similar. 

 The Sand Martin and the Woodpecker, or the Dipper and the 

 Kingfisher, are good examples in which a covered nesting-site 

 is peculiar to each, and the eggs are uniformly white. In 

 cases wdiere the eggs differ considerably from those typical of 

 the group, we generally find that the mode of nidification 

 adopted by the species is from some cause different and 

 aberrant too. Take, for instance, the eggs of the American 

 Quail, which are white and laid in a domed or covered nest ; 

 whilst those of the allied Plumed Quail are normally spotted 

 and blotched, and, it is needless to say, laid in an open nest ! 

 What do we infer from these interesting^ facts ? What do 

 they teach us ? I think they show beyond the possibility of 

 doubt the more or less close relationship of one bird to 

 another, and prove the community of origin of birds in each 

 great natural group, in each family, and in many genera. We 

 have thus seen that birds, aided by a rigorous natural 



^ It is well here to point out that if an egg, say of a Guillemot, is ex- 

 amined, many of the spots will be found to be much paler than the others. 

 This paleness is due to their being covered by a thin coating of shell material, 

 which, if scraped away, will make them appear as rich in colour as those that 

 lie upon the surface. The rich dark class of spots are known as surface 

 markings ; the pale gray ones as underlying markings. 



