BIRDS’ EGGS. 
(See desk-cases in Hall No. 208, and Local Collection, Hall No. 303.) 
Number of Eggs in a “ Set” or “ Clutch.” — The number of eggs 
comprising a full “ set’ or “clutch” ranges from one to as many 
as twenty. No law governing this number is known. Generally 
speaking birds of the same family lay approximately the same 
number of eggs, but there is much variation between birds of 
closely related families (e.g., Loons and Grebes), while birds of 
similar nesting habits may not lay the same number of eggs (e.g., 
Quail and Meadowlark). 
The number of eggs in a set, or clutch, is no indication of 
the fecundity of the bird. At the time of laying the ovary con- 
tains a large number of partly formed eggs, of which, normally, 
only the required number Will become fully developed. But if 
the nest be robbed, the stolen eggs will sometimes be replaced. 
The long-continued laying of our domestic fowls is an instance of 
this unnatural stimulation of the ovary caused by persistent 
robbing. 
Size of Eggs.— The size of the egg depends primarily upon the 
size of the bird. The graduated series, from an Ostrich to a Hum- 
mingbird (Alcove No. 3, Hall No. 208) represents the range of 
variation among the eggs of living birds. Size, however, is further 
influenced by the condition of the young when hatched. Preeco- 
cial birds, for example, the domestic fowls, lay relatively larger 
eggs than altricial birds, for example, Pigeons. 
This will be appreciated by comparing the egg of the Crow 
with that of Wallace’s Megapode, or the eggs of the Meadowlark 
with those of the Bartramian Sandpiper (See desk-case, Alcove 
No. 3, Hall No. 208). The young of the Crow and the Meadow- 
lark are hatched naked and are reared in a well-formed nest. 
The Sandpiper lays its eggs in a slight depression in the ground, 
and its young run about soon after birth. The Megapode buries 
its egg and leaves it to be hatched by the heat generated by 
decay of the vegetable debris in which it is placed. The young 
are born fully feathered and ready to fly. 
IL 
