facts. In 1893 Saint Loup (28 p. 85) advanced the opinion that dancing
individuals appear from time to time among races of common mice. The
peculiarity of movement may be due, he thinks, to an accidental nervous
defect which possibly might be transmissible to the offspring of the
exceptional individual. Saint Loup for several months had under
observation a litter of common mice whose quick, jerky, nervous movements
of the head, continuous activity, and rapid whirling closely resembled the
characteristic movements of the true dancers of China. He states that
these mice ran around in circles of from 1 to 20 cm. in diameter. They
turned in either direction, but more frequently to the left, that is,
anticlockwise. At intervals they ran in figure-eights ([Symbol: figure
eight]) as do the true dancers. According to Saint Loup these exceptional
individuals were healthy, active, tame, and not markedly different in
general intelligence from the ordinary mouse. One of these mice produced a
litter of seven young, in which, however, none of the peculiarities of
behavior of the parents appeared.

In view of this proof of the occurrence of dancing individuals among
common mice, Saint Loup believes that the race of dancers has resulted
from the inheritance and accentuation of an "accidental" deviation from
the usual mode of behavior. It is scarcely necessary to say that this
opinion would be of far greater weight had he observed, instead of
postulating, the inheritance of the peculiarities of movement which he has
described. It might be objected, to the first of his so-called facts, that
the litter resulted from the mating of mice which possessed dancer blood.
Until the occurrence of dancers among varieties of mice which are known to
be unmixed with true dancers is established, and further, until the
inheritance of this peculiar deviation from the normal is proved, Saint
Loup's account of the origin of the dancing mouse race must be regarded as
an hypothesis.