98 KINSHIP OF BIRDS, AS SHOWN BY EGGS. 



brilliant pebbly regions, carrying with them the bluish, green- 

 ish, creamy or drab grounds, and by that tendency to variation 

 for which we can never account — a thing as mysterious as 

 life itself — they here, through the agency of natural selection, 

 began a mottled color-adaptation which has developed so 

 highly in our shore birds, Gulls and their relations. 



Among the tree-builders, Mr. Wallace has suggested that 

 the mottling might be produced by the same sort of imita- 

 tion of the light and shadow spots, caused by the sun's rays 

 being strained through the foliage. But this seems too 

 uncertain to satisfy us. With the 0.2,^, coloration developed 

 from the other way, we can see how this might slightly 

 intensify the already inherited tendency of spotting and 

 modify the tints. This view would tend to account for the 

 blue and green grounds persisting. I am inclined to feel, 

 however, that the basis of many highly spotted eggs of tree- 

 builders is purely hereditarj\ I cannot see, for instance, 

 how natural selection could get hold of the wreath around 

 the large end of so many high grade eggs. It must be the 

 remains of a reversion. 



Perhaps no group of birds are akin to so many others, 

 either by progression or retrogression, as the Limicolce. 

 That they were closely connected to the Gulls I found out 

 in an attempt to differentiate their eggs and nidification by 

 mere descriptions independent of the birds, long before I 

 had noted that this relationship had been asserted of their 

 structure. If, as held by some, the A/ddce (Auks, Murres, 

 Puffins, etc.) are degenerated from the Limia)/i£, through the 

 Gulls {Laridce) we may readily see why the eggs of so many 

 AkidiS are so heavily marked, though deposited now in 

 burrows. Here, it would seem, a circuitous route to a con- 

 cealed nest is fairly indicated ; for if these eggs had gone 

 directly from beneath the sand to a burrow they might have 

 remained white. 



Among the Birds of Prey, the markings as noted are quite 

 probably an inheritance from the ground-building habits of 



