The Parts of an Egg

The Parts of an Egg

From the USDA Handbook No. 75, July, 1961

---

 

Development of the Chick in the Egg

Before Egg Laying:
--Fertilization
--Division and growth of living cells
--Segregation of cells into groups of tissues

Between Laying and Incubation:
--No growth; stage of inactive embryonic life

During Incubation:
First Day:
16 hours-- First sign of resemblance to a chick embryo
18 hours-- Appearance of alimentary tract
20 hours-- Appearance of vertebral column
21 hours-- Beginning of formation of nervous system
22 hours-- Beginning of formation of head
24 hours-- Beginning of formation of eye

Second Day:
25 hours-- Beginning of formation of heart
35 hours-- Beginning of formation of ear
42 hours-- Heart begins to beat

Third Day:
60 hours-- Beginning of formation of nose
62 hours-- Beginning of formation of legs
64 hours-- Beginning of formation of wings

Fourth Day:-- Beginning of formation of tongue
Fifth Day:-- Formation of reproductive organs and differentiation of sex
Sixth Day:-- Beginning of formation of beak
Eighth Day:-- Beginning of formation of feathers
Tenth Day:-- Beginning of hardening of beak
Thirteenth Day:-- Appearance of scales and claws
Fourteenth Day:-- Embryo gets position suitable for breaking the shell
Sixteenth Day:-- Scales, claws, and beak becoming firm and horny
Seventeenth Day:-- Beak turns toward air cell
Nineteenth Day:-- Yolk sac begins to enter body cavity
Twentieth Day:-- Yolk sac completely drawn into body cavity
Twenty-first Day:-- Hatching of chick