Defining Carnegie Stage Features

Stage 12

Head oval shaped, thick nose, blunt tail, strong optic vesicle appearance

Stage 13

more prominent “snout”, pointy tail, optic vesicle “covered”, limb bud only recognized by a line, looks flush

Stage 14

upper limb bud bean-like but prominent, shallow V for myelencephalon w/darkness above, lower limb seen and kinda circular/involved in the tail

Stage 15

lower limb bud bean-like but prominent, upper limb but joint-like, very pointy and long tail

Stage 16

myelencephalon has prominent V giving neck appearance, eye present, notable head circle on forehead (cerebral vesicle), veiny appearance, lower limb appears separate, tail shorter

Stage 17

can kinda see eyebrow, lower limb looks like 2 balls, liver potbelly, cerebral vesicle less prominent - “under” skin appearance

Stage 18

Sharp V in myelencephalon, basically vertical line w/ metencephalon, hand forming lobed appearance, lower limb in 3 clear parts, round node for tail

Stage 19

less prominent myelencephalon, still see vague straight line, tail receded/more butt looking, can see bump for each finger, leg is drumstick looking

Stage 20

bent elbow, fingers more seen, ear is clear, leg straighter

Stage 21

elbow and wrist bend, toes (small but there), looks like nose+grin from Grinch, less harsh head angle

Stage 22

toes more separate, eyelid ridge, megabrain appearance

Stage 23

really clear toes, normal forehead, penis