44 THE WAY LIFE BEGINS 



folds, and walls. The speed with which the new body is 

 built is due to the rapidity of cell division. Soon there are 

 hundreds of thousands of these rapidly dividing cells. Devel- 

 opment begins in the egg on its way down the oviduct, but 

 does not proceed far until incubation begins. 



The First Day. We are ready now, to look at a series of 

 incubating eggs. Open the upper side of the egg. This is 

 best done by inserting the blade of a pair of small, sharp- 

 pointed scissors and cutting around the upper portion of 

 the egg shell. 1 Toward the end of the first day a small germ- 

 disc will be seen lying upon the top of the yolk. The disc is a 

 network of blood vessels, the first steps in the formation of 

 a circulatory system between the yolk and the growing em- 

 bryo which now appears as an elongated depression in the 

 center of the disc. Figure i, Plate VI. 



The Second Day. The beating of the heart will be seen 

 on the second day. The outline of the head appears and the 

 germ-disc has increased its diameter. 



The Third Day. Figure n shows the state of growth 

 on the third day. The yolk has expanded by absorbing 

 moisture from the outside. The curve of the body is plainly 

 indicated, the head is greatly enlarged, and the eyes well 

 marked. 



The Fourth Day. By this time the wings and legs are 

 budding out from the body, the eyes assume enormous 

 proportion, occupying almost the entire forepart of the head. 



The Fifth Day. The chick seems all head, and the head, 

 all eyes. This is nature's way of looking to the most important 

 organs first. Wings and legs and tail have grown longer. This 

 is about the stage represented by Figure in. 



The Tenth Day and After. If we omit the stages of the 

 four following days, and open an egg on the tenth day — 

 eleven days before hatching — we shall find a whole chick. 

 The yolk and 'white' have been enclosed within the body. 

 By the twelfth day (Figure iv) the chick occupies almost 

 the entire egg, and by the fifteenth day some of the feathers, 



1 The embryo may be best observed if the opened egg is immersed in warm (normal) 

 salt solution. Use one level teaspoonful of salt to one pint of water. The heart will continue 

 to beat for some time when the opened egg is placed in this warm solution. 



