31–32 14 b 5.0–7.0 Upper limbs are paddle-shaped. Lens pits and nasal pits visible. Optic cups present.
33–36 15 7.0–9.0 Hand plates formed. Lens vesicles present. Nasal pits prominent. Lower limbs are paddle-shaped. Cervical sinus visible.
37–40 16 8.0–11.0 Foot plates formed. Pigment visible in retina. Auricular hillocks developing.
41–43 17 11.0–14.0 Digital, or finger, rays appear. Auricular hillocks outline future auricle of external ear. Trunk beginning to straighten. Cerebral vesicles prominent.
44–46 18 13.0–17.0 Digital, or toe, rays appearing. Elbow region visible. Eyelids forming. Notches between finger rays. Nipples visible.
47–48 19 16.0–18.0 Limbs extend ventrally. Trunk elongating and straightening. Midgut herniation prominent.
49–51 20 18.0–22.0 Upper limbs longer and bent at elbows. Fingers distinct but webbed. Notches between toe rays. Scalp vascular plexus appears.
52–53 21 22.0–24.0 Hands and feet approach each other. Fingers are free and longer. Toes distinct but wedded. Stubby tail present.
54–55 22 23.0–28.0 Toes free and longer. Eyelids and auricles of external ears are more developed.
56 23 27.0–31.0 Head more rounded and shows human characteristics. External genitalia still have sexless appearance. Distinct bulge caused by herniation of intestines still present in umbilical cord. Tail has disappeared.

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