evolution. Perhaps the most curious exception is that of the elephants, in
which the testes are abdominal. Here, in consequence of their structure
and massive shape, locomotion in usually a walk, and though they run
occasionally the gait is a trot, not a sustained gallop, and leaping is
out of the question. Sloths which hang from branches upside down have
abdominal testes, but even here they are in a posterior position, between,
the rectum and the bladder, so there has apparently been a degree of
dislocation, probably inherited from ancestors with more terrestrial
habits.

The fact that the ovaries do not occupy normally a position similar to
that of the testes is in accordance with the theory, for they are very
much smaller than the testes; and yet they have undergone some change of
position, for they are posterior to the kidneys.

The facts agree with the hormone theory, for it is to be noted that
although the development of the scrotum is confined to the males, the
'descent' or dislocation takes place in the foetus, and not at the period
of puberty. This is in accordance with the fact that the mechanical
conditions to which the change is attributed are not related to sexual
habits, but to the general habits of life which begin soon after birth.
The development, therefore, may be considered to be related to the
presence of a hormone derived from the normal testis, but not to a special
quantity or quality of hormone associated with maturity or the functional
activity of the organ. In Rodents, however, there is a difference in the
organs, not only at maturity, but in every rutting season, at any rate in
Muridae such as rats and others. In the rutting season the testes become
much larger and descend into the scrotal sacs, at other times of the year
being apparently more or less abdominal. In rabbits and hares, which have
a much more impulsive progression, the organs seem to be always in the