The most prominent reversional tendencies occur in the genitals. One very
common condition is retention of the testicles within the abdomen
(_cryptorchidism_), which has been already pointed out, and may represent
the last expiring trace of degeneracy. The testicles may, however, be
perfectly normal in structure and function. In the female the uterus may
present every type of mammalian uterus from the marsupial up. The female
may also revert (as more rarely the male) to the condition of the reptiles
and oviparous mammals in which the urinary organs and bowels empty into a
single opening, the cloaca. This condition has been found in the female
offspring of degenerate families, who are otherwise normal and who have
produced children, despite the cloaca.