embryonic

Both sets of eggs were handled in the same manner and under the same conditions in the same environment. These are the control variables in my experiment.

I recorded the weights, and lengths, of both the fresh and refrigerated “test” eggs using a beam balance every 5^th day. Using a small piece of aluminum foil to cradle the egg was helpful during this process. To weigh the egg I needed a counterweight that was easy to work with so I used nickels because they weigh exactly 5 grams.

A period of 10 -15 minutes out of the incubator will not damage the embryos. When candling, if the embryo is alive and circulation is established, the contents of the egg will have a pinkish color. But, if the embryo is dead, the content will appear muddy or brownish. The growing embryo eventually occupies the entire interior of the egg and the candler can no longer transmit light; thus, it is impossible to see anything but the air cell by the 16th day. Infertile eggs appear clear and early dead embryos, called quitters, can be detected readily because they appear as a dark black spot.

I candled the eggs on 13 separate occasions but stopped on day 14 so not to harm the chicks. I also stopped turning the eggs at that time. After day seventeen I did not open the incubator except for weighing “test” eggs a final time. It is important to only observe near the end of incubation.

Candling at Day 0 showed only the presence of yolks in the eggs. I weighed the three “test” eggs from each set. As the Measuring Chart illustrates, their weights were between 39.5-65 grams. I was able to see the beginning of the formation of a dark area attached to the yolk sac and spider veins in most eggs by day 3. When I detected a dark ring of bacteria, an infertile egg or a blood spot I removed the egg from the box and recorded my findings. On Day 5, I could plainly see the veins running away from the living embryos and the blackness of their eyes.

As each passed, I could see more features and movement inside the eggs. The hatching process took from 4 to 18 hours. One chick hatched a day later with little problems. When the chick frees itself from the shell it appears wet and very tired and for the next several hours it sits still and rests. A few hours later the chick is dry and extremely active and the egg tooth dries up and falls off.

EMBRYONIC DEVELOPMENT:

Inside the hen there is an ovary that contains thousands of tiny, undeveloped egg yolks. One at a time, these egg yolks develop and grow larger. When a yolk is mature, it is released into the oviduct, which is the tube that carries the egg from the ovary to outside the hen. As the yolk goes down the oviduct it is fertilized (about 24-hours prior to laying) and egg white begins to close around it. It is then wrapped in membranes and finally enclosed in the shell before the hen drops the egg. A hen requires 24 to 26 hours to produce an egg. Thirty minutes later the process begins all over again.

Growth and development:

Soon after incubation is begun, a pointed thickened layer of cells becomes visible in the caudal or tail end, of the embryo. Before the first day of incubation is through, many new organs are forming. The head of the embryo becomes distinguishable, the eye and digestive tract begins to form and blood islands appear that will develop into the vascular system.

Stages of development:

THE FIRST DAY:

Nervous system begins to develop and within 16 hours the first sign of resemblance to a chick embryo is seen. By 22 hours of life the beginning of the head and eyes are forming.