168 THE LIFE OF A BIRD. 



sticks from every accident of wind and weather ! 

 Hence it appears obvious, that preparation must 

 be made in the shell for the circumstances to 

 which the future being is to be exposed, in the one 

 case ; while in the other, as it is to be long under 

 parental care, no such preparation is necessary, 

 the accidents to which, in the latter case, it is 

 exposed, being few and trifling in their nature, 

 compared to those which the former lie at the 

 mercy of. That this development in the shell 

 requires a larger amount of space than is required 

 when it proceeds to a lower degree, is obvious. 

 Yet, in consequence of the peculiar form of the 

 egg as adapted to that of the future body it is 

 intended to contain, very little space is lost ; and 

 the parent bird, when incubating the largest eggs, 

 is well able to cover them so as efficiently to sup- 

 ply the necessary degree of animal heat. 



Let us glance at the absolute size of various 

 eggs, without reference to that of the bird. That 

 of the great auk, the size of which has just been 

 given, must be taken as the largest among British 

 birds. Of existing species, that of the ostrich is 

 undoubtedly the largest. Its shell is very dense 

 and strong; and it weighs sometimes as much as 



