58 PROGRESSIVE POULTRY CULTURE 



the picture so that soon only an opaque oval form shows 

 before the tester, except for the clear area of the air-cell 

 and narrow space below it, which still allows some light 

 to percolate through and permits the movements of the 

 embryo to be detected. The air-cell enlarges rapidly 

 during the last week of incubation because of the escape 

 of the waste products of growth through the shell. 



At the close of the fourteenth day, if any of the eggs 

 show, before the tester, areas on one side or at the small 

 end that are clear or yellowish instead of dark opaque, 

 these eggs should be marked and especial care taken 

 to note whether they hatch or not and if they do hatch 

 what sort of chicks come from them. This appearance 

 is usually due to the folding back of the veins or their 

 failure to occupy the areas which lack opaqueness. 



By the end of the nineteenth day some of the eggs 

 placed before the tester, may show a perfectly opaque 

 oval, due to the chick having burst through the inner 

 membrane and occupied the space of the air-cell. In 

 this case he has begun to breathe with his lungs and 

 may very likely be heard to peep in the shell occasion- 

 ally. 



On the twentieth day most of the chicks in the 

 shells should burst their barriers and begin life outside 

 the shells. All the live chicks should certainly be 

 hatched by the end of the twenty-first day. 



Any eggs that fail to hatch should be looked at be- 

 fore the tester and then be broken open and examined 

 critically, to learn, if possible, the reason of their dying 

 in the shell. 



In eggs showing areas of albumen not covered with 

 veins, the chicks may have failed to complete their 

 growth or possess too little strength to hatch because 

 of lack of sufficient nourishment. Possibly this con- 

 dition may trace back to lack of vigor in the parent 

 breeding stock or to their improper feeding. If this is 

 not the case there may have been too high a temperature 

 maintained in the first days of incubation or too low 

 a temperature in the under parts of the eggs. 



Sometimes the chick succeeds in breaking through 



