Here are the stages in development explained.
IMPORTANT EVENTS IN EMBRYONIC DEVELOPMENT
BEFORE EGG LAYING
Fertilization
Division and growth of living cells
Segregation of cells into groups of special function
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
23 hours - Appearance of blood islands - vitelline circulation
24 hours - Beginning of formation of eye
SECOND DAY:
23 hours - Beginning of formation of heart
35 hours - Beginning of formation of ear
42 hours - Heart begins to beat
THIRD DAY:
50 hours - Beginning of formation of amnion
60 hours - Beginning of formation of nose
62 hours - Beginning of formation of legs
64 hours - Beginning of formation of wings
70 hours - Beginning of formation of allantois
FOURTH DAY:
Beginning of formation of
FIFTH DAY:
Beginning of formation of reproductive organs and differentiation of sex
SIXTH DAY:
Beginning of formation of beak and eggtooth
EIGHTH DAY:
Beginning of formation of feathers
TENTH DAY:
Beginning of hardening of beak
THIRTEENTH DAY:
Appearance of scales and claws
FOURTEENTH DAY:
Embryo turns its head toward the blunt end of egg
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; embryo occupies practically all the space within the egg except the air cell
TWENTY-FIRST DAY:
Hatching of chick
