I do have a turner but I incubate in a cabinet incubator. A couple of times I had marked the wrong week on my calendar and the chicks started hatching in the turners. I still had great hatches.
Here is a website with some interesting pictures of an egg developing.
http://www.the-chicken-chick.com/2012/03/chicken-embryo-development-views-from.html
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 tongue
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