Sex determination in mammals is mediated via the supporting cell lineage in the fetal gonad. In the very early stages of gonadal development, the fate of the supporting cell population is critically dependent on the expression of the male‐determining gene on the Y chromosome. If this gene is absent or fails to be expressed, or is expressed too late or in too small a number of supporting cells, all supporting cells (XX or XY) differentiate as pre‐follicle cells and development proceeds (...) along the female pathway. Supporting cells in which the male‐determining gene is expressed in a timely manner differentiate as pre‐Sertoli cells; given sufficient such cells, testis cords form and development proceeds in a male direction. If XX supporting cells are also present, a few may be recruited into the pre‐Sertoli population and participate in testis cord formation. The subsequent fate of pre‐follicle cells depends critically on interaction with the germ cell population in the developing gonad: absence of germ cells may lead to partial masculinization of the gonad, and/or to disappearance of the supporting cell component. (shrink)

In Lewis Carroll's AliceThroughtheLooking-Glass, Humpty Dumpty said: neither more nor less.” One may not agree with this approach, but it may well be preferable to using a word: (a) with only a vague idea of its meaning, or (b) with many possible meanings.

In 1822, Alexander Berry (1781–1873), a recent free settler in the early colony of New South Wales (N.S.W.), read a paper on the geology of the coast of N.S.W. to the newly formed Philosophical Soc...