The Descent of Man

counter a singular difficulty. In the mammalian
class the males possess rudiments of a uterus
with the adjacent passage, in their vesiculae
prostaticae; they bear also rudiments of mammae,
and some male Marsupials have traces of
a marsupial sack. (27. The male Thylacinus offers
the best instance. Owen, 'Anatomy of Vertebrates,'
vol. iii. p. 771.) Other analogous facts
could be added. Are we, then, to suppose that
some extremely ancient mammal continued
androgynous, after it had acquired the chief
distinctions of its class, and therefore after it
had diverged from the lower classes of the vertebrate
kingdom? This seems very improbable,
for we have to look to fishes, the lowest of all
the classes, to find any still existent androgynous
forms. (28. Hermaphroditism has been
observed in several species of Serranus, as well
as in some other fishes, where it is either normal
and symmetrical, or abnormal and unilateral.
Dr. Zouteveen has given me references on
this subject, more especially to a paper by Prof.