EGG 



1960 



EGG 



IGG. There is an old question which in 

 times gone by wise men did not scorn to 

 puzzle their brains about, and which even to- 

 day is occasionally propounded just to cause 

 confusion "Which came first, the hen or the 

 egg?" It is a question which admits of no 

 answer, for each is absolutely essential to the 

 existence of the other. In all ranks of life 

 above the very lowest, where reproduction 

 takes place by simple division, it is impossible 

 for young animals to be produced except from 

 eggs. In the highest of all classes, the mam- 

 mals (which see), it takes the egg a long time 

 to develop, and it remains in the body of the 

 female until it is hatched. Even then the 

 young animal is not brought forth at once, 

 but is sheltered within the body of the mother 

 until it has partially matured. 



But in far more numerous cases animals lay 

 their eggs to be hatched later, and it is eggs 

 of this sort which are ordinarily meant when 

 the term is used. Worms, mollusks, insects, 

 fishes, birds, reptiles all these are egg-laying 

 animals; and though their eggs differ in size, 

 in shape and even in their constituent parts, 

 they are all alike in one thing. 



What Is an Egg? This one thing which all 

 eggs must possess is the embryo, nucleus, or 

 germ, from which the young animal develops. 

 It is always small, and frequently so tiny as 

 to be almost invisible, but it is the only part 

 of the egg which has in it the possibility of 

 life. All the other parts, frequently bulky in 

 proportion to the size of the nucleus, are for 

 food and for protection. The eggs of insects 

 and of many of the lower animals, frequently 

 produced in amazing numbers, are imperfect 

 that is, they do not possess the protective 

 coverings which form part of the eggs of birds. 

 If they did, and thus escaped in larger meas- 

 ure the destruction which waits for them on 

 every side, the world would literally swarm 

 with the young which would come from them. 



A Typical Egg. Most perfect and most 

 interesting, as well as of most importance 

 commercially, are the eggs of birds. A bird's 



egg consists of five parts: (1) the shell; (2) the 

 double membrane lining the shell; (3) the 

 white; (4) the- yolk; and (5) the germ. 



(1) The shell, which usually makes up about 

 eleven per cent of the weight of the egg, is 

 formed almost wholly of carbonate of lime. 

 The eggs of some birds are as smooth and 

 shiny as enamel, while others are dull and 

 rough; some are white, or nearly so; others 

 exhibit exquisite tints and markings, such as 

 the olive-brown spots on the grayish-white 

 eggs of the bobolink, or the reddish-brown 

 marks on those of the meadow lark; but in 

 any case they all fulfil their one purpose, 

 which is that of protection. The smaller the 

 bird, the thinner the eggshell is likely to be, 

 for a tiny humming bird could not possibly 

 peck its way through the thick covering from 

 which the young ostrich chick emerges with 

 ease. 



(2) The thin, tough membrane which lines 

 the shell and gives it added strength is some- 

 what felty and elastic. As stated above, it is 

 double, and at one end the two layers are 

 widely separated, an air-chamber filling in the 

 space between the two. This air, it is be- 

 lieved, is breathed by the little chick while 

 it is pecking its way out. 



(3) The albumen, or white, a food layer 

 which contains a large proportion of water, 

 has running through it two threads, or 

 chalazae ; everybody has noticed them, with 

 impatience, probably, in a soft-boiled egg. 

 Their function is to hold the yolk in its place 

 in the surrounding white, and they are able 

 to perform this steadying task because they 

 are fastened to the lining membrane. 



(4) The yolk, a yellow ball surrounded by 

 a thin, transparent membrane, is composed of 

 one cell, the largest single- cells known being 

 the yolks of the larger birds' eggs. This yolk 

 is a very rich, concentrated food, easy of di- 

 gestion by the developing birdling. 



(5) Near the surface of the yolk on one 

 side, and plainly visible in an egg which has 

 not been brooded, is a circular white patch 



