The Descent of Man

horses, asses, and mules, dark- coloured stripes
suddenly reappear on the legs, and shoulders,
after an interval of hundreds, or more probably
of thousands of generations.
These various cases of reversion are so closely
related to those of rudimentary organs given in
the first chapter, that many of them might have
been indifferently introduced either there or
here. Thus a human uterus furnished with cornua
may be said to represent, in a rudimentary
condition, the same organ in its normal state in
certain mammals. Some parts which are rudimentary
in man, as the os coccyx in both sexes,
and the mammae in the male sex, are always
present; whilst others, such as the supracondyloid
foramen, only occasionally appear, and
therefore might have been introduced under
the head of reversion. These several reversionary
structures, as well as the strictly rudimentary
ones, reveal the descent of man from some
lower form in an unmistakable manner.