i66 NATURAL SCIENCE. march, 



the Scops Owl, to different modifications of elliptical or oval. The 

 latter form, in which one end is smaller and more pointed than the 

 other, though not universal, is the most frequent, and distinguishes 

 the eggs of birds from those of reptiles. If there are many eggs in 

 the nest it is obvious that the conical form makes close packing more 

 easy. Where only two eggs are laid they are seldom conical. Eggs 

 having a pyriform shape, or narrowing very rapidly towards the 

 smaller end are mostly those of wading birds [Limicolcd) which lay 

 four in a nest, and are large in proportion to the size of the bird, as 

 exemplified by four Lapwing's eggs. Their pointed ends being turned 

 inwards, they occupy as little space as possible, and are thus more 

 easily covered by the brooding parent. A conical egg placed on the 

 ground or a ledge of rock is less liable to roll away from its place if 

 disturbed, than one of a spherical form. The size of the egg has 

 generally, but by no means constantly, some relation to that of the 

 parent bird. It also depends very much on the degree of develop- 

 ment of the young bird at the time of hatching. When the hatched 

 young are immature and helpless the eggs are small relatively to the 

 size of the parent. Such birds usually build carefully-constructed 

 nests. But when the young are well clothed with down and can run 

 and feed themselves, the eggs are large, and laid on the ground or in 

 imperfect nests. The Curlew and Raven are instances of birds of 

 equal size with differently-sized eggs. The Cuckoo, which lays eggs 

 in the nests of birds smaller than itself, has a relatively smaller egg 

 than any other bird. The surface of the shell varies much in texture 

 in the eggs of different birds. Among other examples are the smooth 

 polished egg of the Tinamou, the smooth and glossy egg of 

 the Kingfisher, the dull and chalky eggs of the Ibis and Duck, 

 the eggs of the Ani and Flamingo with a distinct calcareous film, 

 and the rough, pitted egg of the Emeu. The colour of the egg 

 has no relation to that of the parent bird. White is probably 

 the primitive colour of birds' eggs, as it is that of the eggs of 

 all reptiles. The eggs of birds laid in holes, either in the earth or 

 trees, entirely concealed from the light, are mostly white. The larger 

 number of eggs are variously coloured by the deposition of pigment 

 on or near the outer surface of the shell. The colour may be uniform 

 throughout the surface of the shell, or it may be in irregular washes, 

 blotches, more or less circular spots or lines, upon either a white or 

 uniformly coloured ground. The signification of the various modes of 

 colouration is very little understood at present. It often happens that 

 the different species of a natural group of birds present a general 

 similarity in the style of colouration of their eggs, or in other words 

 that nearly-allied birds have similar eggs, a fact exemplified by sets 

 of Warblers' and Buntings' eggs ; but the exceptions to this rule are 

 very numerous as shown by eggs of different species of Thrush. In 

 certain cases there is evidently an adaptation of the colour of the eggs 

 to their natural surroundings for the purpose of concealment. Excel- 



