ON THE EGG. 259 



are some white eggs that are not eaten — others have a uniform 

 ground colour of blue, green, yellow, pink, red, orange, or brown, 

 or, in short, of almost any shade of colour but without any spot- 

 ting or marking. Others again, whether white or of any ground 

 colouring, are variously spotted or streaked or blotched. Now, 

 these colours are exactly the same as we see on our own skins 

 that have been violently bruised with effusion of blood ; Eor ex- 

 ample, witness what occurs in case of a black eye in its course 

 towards recovery, — at first it is "black and blue" and may be 

 bloody, and by degrees passes through the same series of colour- 

 ing that may be observed in a series of coloured eggs of birds, 

 ending in the faintest yellow, — a succession of colours known to 

 the fighting school-boy. As these colours in the human skin are 

 due to blood effused from ruptured blood-vessels, to the inflam- 

 mation or congestion caused by the blow, and to the changes 

 undergone in the blood and serum effused, during their absorp- 

 tion, so the colours of the eggs of birds are due to the inflam- 

 mation or congestion of the mucous membrane of the oviduct 

 and to the effusion of blood from ruptured blood-vessels upon 

 the plaster covering, or shell of the egg. 



"We now come to the making up of the egg of a hen or other 

 bird. The parts immediately concerned in this process are the 

 ovarium and the oviduct. The ovarium is a most delicate trans- 

 parent membranous bag attached to the spine of the bird, and 

 is full of yellowish-orange coloured cells or globules of different 

 sizes, or ova in different stages of development. These are in- 

 cipient yolks of future eggs, and in each ovum when mature 

 there is to be found a very small vesicle, but one much larger 

 than the rest of the globules with which the coloured yolks are 

 filled. In this small vesicle is another still smaller. The former 

 is named the "germinal vesicle," the latter the "germinal spot," 

 These are the essential — the living parts of the egg in which 

 evolution commences. Eelow the ovarium and attached to it is 

 the top of the oviduct, which is a starlike opening into a rather 

 tortuous tube, extending to the posterior part of the body, where 

 it ends in a dilatation that leads to the exterior. The oviduct 

 is a muscular contractile tube, lined by delicate mucous mem- 



