2 STEUCTURE OF THE EGG. 



themselves indifferent conductors of heat, but entangle among their multitudinous fibres 

 a considerable amount of air, v/hich resists the ingress or the egress of external or 

 internal heat, and thus preserves the bird in a moderate temperature through the icy 

 blasts of winter or the burning rays of the summer sun. A similar function is discharged by 

 the furry coats of many mammalia ; but the feathers serve another oflPice, which is not 

 possessed by hair or fur. They aid the creature in progression, and enable it to raise 

 and to sustain itself in the atmosphere. Towards the promotion of this latter function 

 the entire structure of the body and limbs is obviously subservient, and even in the 

 comparatively rare instances where the bird — such as the penguin, ostrich, or the 

 kiwi-kiwi— is destitute of flying powers, the general idea of a flying creature is still 

 preserved. 



The fuller and more technical description of the Birds runs as follows. They are 

 vertebrate animals, but do not suckle their young, nourishing them in most instances 

 with food which has been partially macerated in their own digestive organs, and which 

 they are able to disgorge at will, after a manner somewhat similar to that of the 

 ruminating quadrupeds. The young are not produced in an actively animated state, but 

 inclosed in the egg, from which they do not emerge until they have been warmed into 

 independent life by the effects of constant warmth. Generally, the eggs are hatched by 

 means of the natural warmth which proceeds from the mother bird ; but in some instances, 

 such as that of the tallegalla of Australia, the eggs are placed in a vast heap of dead leaves 

 and grass, and developed by means of the heat wliich is exhaled from decaying vegetable 

 substances, and which is generated to such an extent that in some cases, such as a wet 

 haystack, it actually sets the seething mass on fire. Urged by a like instinct, our common 

 English snake deposits its eggs in secret spots, such as dunghills and hotbeds, and 

 there leaves them to be hatched by the constantly generated warmth. An analogous 

 process has long been in vogue among the Egyptians for the hatching of young 

 poultry by artificial heat, and has been, in comparatively recent years, introduced into 

 this country. 



When the egg is first produced, the future chicken is merely indicated by a little 

 germ-spot, barely the size of a single oat-grain, and does not attain the power of breathing 

 atmospheric air, and receiving nourishment into its mouth, untO. a period of many days 

 has elapsed. To watch the gradual development of the young chick is a most 

 interesting experiment, and one which is full of suggestive instruction. There is but 

 little difficulty in the matter, even in the very earliest stages of incubation, for the 

 structure of the egg is so wonderfully balanced, that in order to view the little germ-spot 

 it is only necessary to lay the egg on its side and remove a portion of the shell, when the 

 germ will be seen lying immediately under the aperture. In whatever way an egg may 

 be turned, the germ-spot invariably presents itself at the highest point, provided only that 

 the egg be laid on its side, and that the living principle has not been extinguished, for life, 

 however undeveloped, seems always to aspire. As the chick increases in size, the 

 manipulation becomes easier, but it is always better to immerse the egg in water or 

 other transparent liquid before removing the shell, and to keep it submerged during 

 examination. 



There are few objects which will better repay investigation than the young bird in its 

 various stages of development. It is so wonderful to see the manner in which a living 

 creature is gradually evolved from the apparently lifeless substances that are contained 

 within an egg. The being seems to grow under our very gaze, and we arise from the 

 wondrous spectacle with an involuntary feeling that we have been present at a veritable 

 act of creation. To describe fully the beautiful process in which a chick is elaborated out 

 of the germ-spot would occupy very many pages, and cannot be attempted within the 

 compass of the present work. Briefly, however, the order of events is as follows. 



Wlien a newly laid egg is opened, it is found to contain a mass of substance which is 

 popularly divided simply into " white " and " yolk," but when examined more closely, by 

 placing it under water and carefully removing the shell, its contents are found to be 

 very elaborately disposed, so as to meet the object for which it was formed. Immediately 

 within the shell lies a semi-transparent and tolerably strong membrane, composed of two 



OSI 



