238 MR J. B. DOBBIE ON 
laid by different species of birds—and even by some which 
are nearly related—varies greatly. Many birds, chiefly sea 
birds, lay only one egg, while others, such as the Pheasant 
and Partridge, occasionally lay twenty or more. The common 
Cuckoo is still more prolific, for it has been proved that each 
female lays not fewer than twenty eggs annually; but even 
this fecundity is far surpassed in the case of the Silky Cow- 
bird (Molothrus bonariensis), for, according to the valuable 
testimony of Mr W. H. Hudson, each female certainly lays 
thirty-two eggs, and probably double that number, during the 
season. 
3. THe Form OF THE EGG. 
That the shape of the egg varies greatly is at once obvious 
to any one who glances at the contents of a moderate collec- 
tion. Still following the South Kensington model, the egg 
may be either elliptical or oval, but both these figures are 
subject to considerable modification. Thus we have spheroi- 
dal (Bee-eater), elliptical (Sand Grouse), long ellipse (Shag), 
biconical (Sclavonian Grebe), true oval (Partridge), conical 
(Water Pheasant), and elongated conical (Guillemot). But 
while, as a rule, the eggs of each family at least closely 
resemble each other in shape, there are some striking ex- 
ceptions. Among Passerine birds, for example, the eggs of 
the genus AXgithalus (Penduline Tits) are in shape not only 
widely different from those of the other members of the 
Family, but also from the normal type of eggs of birds 
belonging to the same Order. On the other hand, they are 
strikingly like eggs of certain species of Swifts and Wood- 
peckers, birds which belong to totally different Orders. So far 
as individual species are concerned, the greatest variation in 
the shape of the egg is to be found among the Galliformes ; 
but the reason for this must be obvious. It is by no means, 
however, so easy to tell why the eggs of the Alucine (Barn 
Owls) should differ so markedly in shape from those of all 
other Owls. But that the Owls are divided into two widely 
divergent groups is known from anatomical and pterylological 
as well as from oological research. Many other instances 
might be adduced to show how greatly the eggs of birds 
