14 EGGS AND EGG-COLLECTING. 
Thirdly, the number of eggs is always four, and by 
such limitation the form of the square is preserved, 
and the difficulty of a small bird covering a number of 
large eggs satisfactorily surmounted. I have often dis- 
arranged the order of Plovers’ eggs, but always found that 
the first thing done by the bird on her return was to 
reduce chaos to order by turning the round ends out and 
the small ones into the centre of her little household. 
Lastly, we come to the beautiful harmony of colouring 
of the eggs with surrounding objects, rendering them often 
very difficult to find, even by a practised eye, and the 
scant nest still further aiding in the chances against dis- 
covery. 
The Sandpiper affords an admirable instance of the 
assimilation of its eggs to surrounding objects, and the 
extreme difficulty experienced in finding them attests to 
its protective utility. 
Why Eggs Vary so much in Point of Number.— 
The number of eggs laid by birds of different orders 
seems to be regulated by the danger to which they are 
exposed and the amount of food which the parents will be 
able to supply. 
Thus, the Eagle in its inaccessible eyrie enjoys almost 
perfect immunity from danger, and has only two young 
ones, for which, however, the supply of food is only equal 
to the demand, and it is probable that one more voracious 
appetite would seriously endanger the safety of the whole 
fathily. 
On the other hand, take the Common Partridge with 
its sixteen or twenty eggs, the high percentage of its 
dangers, and the generally abundant supply of food. 
Again, the Swift, on its untiring wings for sixteen 
