8 



The various typical forms may be classiaed under the following 

 heads : — 



Ovoid, Pyriform, Bi- Conical, Oval, Cylindrical and 

 Spherical. 



Ovoid.— The most familiar form is ovoid, that being the shape of 

 the eggs of the Domestic fowl and of nearly all Game birds {Galli- 

 formcs), also of the Gulls (Lariformes), Ducks (Anseriformes), and 

 of most Perching birds (Passeriformcs). 



Pyriform. — Pear-shaped or pyriform eggs are especially charac- 

 teristic of the Snipe, Plovers, and Sandpipers (Charadriiformes), the 

 Guillemots and Great auk {Alciformes), 



-Nearly all of the Snipes, Plovers, and SandjDipers lay four eggs 

 in a nest, where they lie with points to the centre, thus occupying 

 as little space as possible and being more easily covered by the 

 brooding parent. 



The Guillemot lays but one egg on a ledge of bare rock, no nest 

 being made. The pyriform shape of the egg prevents it from 

 rolling far. A knock or a rough wind only causes it to revolve, or 

 roll iu a small circle. 



Bi-conical. — Eggs pointed at both ends or bi-conical are charac- 

 teristic of the Grebes {Podicejoedidiforrr.es). 



Oval. — The eggs of the Nightjar {Caprimulgus europceus) have 

 both ends equally rounded, forming an almost true oval. 



Cylindrical. — The eggs of the Sand grouse [Pterodeidcr) are 

 elongated and almost cylindrical and bluntly rounded at each end. 



Spherical — Eggs very nearly spherical are characteristic of the 

 Owls iStriges) and some of the Picarian birds, as, for example, the 

 Bee-eater {Merops apiasier) and the Kingfisher (Alcedoisinda). 



The eggs of most birds of prey (Accipitriformes) approach this 

 form. 



GRAIN OF THE EGG-SHELL. 



In certain families of birds the egg-shell exhibits a definite 

 grain or texture which may be easily recognised, especially when 

 magnified. 



A difference of grain is in some cases distinctly visible even 

 between species of the same genus {see Specific Differences). 



According to the fineness or coarseness of the grain birds' eggs 

 have a glossy or a dull appearance. 



