The human foetus after 14 weeks, surrounded by the fluid-filled amniotic sac. The foetus is recognisable as the infant it will become, though the head is still out-of-proportion large. Facial features are evident, the eyes have migrated from the sides of the head, & the nose, mouth, & ears have formed. The upper limbs are more developed than the lower ones: the wrist, forearm & fingers are obvious. The abdomen grows rapidly during this time, with the large dark mass being the liver, greatly enlarged to produce red blood cells until the bone marrow (as yet undeveloped) takes over this function. Sexual differentiation has occurred: external male genitalia may be seen.