External: Invagination of the lens disc but with an open lens pit; a well-defined endolymphatic appendage; elongated and tapering upper limb buds.

Internal: The ventral pancreas (if not detectable earlier) is distinguishable at stages 14 and 15; right and left lung sacs grow dorsad; the ureteric bud acquires a metanephrogenic cap; future cerebral hemispheres and cerebellar plates begin to be visible.

Exterior View	Interior View

• Length: 5 - 7 mm
• Invagination of optic lens
• Ear vesicle has well-defined endolymphatic appendages
• Mandibular and hyoid bars have acquired ascendancy over third or gloss pharyngeal bar
• Arm buds elongating and curved toward body.
• Leg buds are fin-like.
• Ovulation age: 31 - 35 days

Question: What structure becomes well defined in the ear
vesicle?

Developmental Stages in Human Embryos by Ronan O'Rahilly and Fabiola Müller.  Published by Carnegie Institution of Washington, Publication 637. 1987. Stage 14 (PDF)

Stage 13

Stage 15 Stage 14 Internal