The germ cells, which will eventually inhabit
the gonads, originate from the primitive
hind gut. They appear around the 25th day.
By 30 days, the gut, complete with its
mesentery, is formed. The germ cells now
migrate from the gut to the root of the
mesentery. Of the original 6 or 7 million,
only 1–2 million are present at birth and this
number is reduced to 300,000 at puberty.
A smaller number of these cells may be a
factor that leads to premature menopause.