110 HATCHING AND REARING 



throws the cap off. After rupturing the shell the chick 

 usually lies quiet for a while to recover its strength, and get 

 ready to walk. During hatching the feathers or down are 

 encased in little oily sacs, which, after the chick breaks the 

 shell, quickly dry out and become very fluffy and soft. A 

 normal chick requires about an hour to an hour and a half 

 to get out of the shell after it has begun to pip. A good 

 hatch should start on the evening of the twentieth and be 

 entirely over by noon of the twenty-first day. 



LABORATORY EXERCISE 



EXERCISE No. 18. Select four uniform eggs and place 

 them under a sitting hen or in an incubator. In six days 

 place four more eggs with those previously set. In six more 

 days place still four more eggs with the previous ones. When 

 the eggs are placed in the nest the date on which they are set 

 should be plainly written on the shell. The eggs selected 

 must come from a flock in which a male bird is kept. ' Eight- 

 een days from the time that the first four eggs are set all 

 of them can be removed and taken into the classroom. After 

 carefully breaking the shell the contents of each egg should 

 be poured into a clean white saucer, each dish being labeled 

 with a paper showing the date the egg was set. From this 

 date the pupil can determine the age of the embryo. By 

 the aid of a wooden toothpick it is a simple matter to separate 

 the embryo from the egg mass. First with the naked eye 

 and later with the aid of a small hand lens allow the class 

 to study the different embryos, locating the different organs 

 which are mentioned in the text. After the study has been 

 made the class should be encouraged to make pencil drawings 

 of what they see. Infertile eggs will frequently be found 

 and they can be compared with the fertile egg. If facilities 

 are available, some of the embryos may be preserved in 

 alcohol for museum samples. 



