The Dancing Mouse | Page 7

white varieties which are brought from the Straits are often kept by the Chinese (p. 637).
The statements of Kishi, Mitsukuri, and Hatai which have been quoted, taken in connection with the opinions expressed by various European scientists who have studied the dancer, make it seem highly probable that the race appeared first in China, and was thence introduced into Japan, from which country it has been brought to Europe and America. Accepting for the present this conclusion with reference to the place of origin of the dancer, we may now inquire, how and when did this curious freak, as Professor Mitsukuri has called it, come into existence? Concerning these matters there is wide divergence of opinion.
Haacke (6 p. 514), as quoted in Brehm's "Tierleben," says that an animal dealer with whom he discussed the question of the possible origin of the dancer maintained that it came from Peru, where it nests in the full cotton capsules, arranging the cotton fibers in the form of a nest by running about among them in small circles. Hence the name cotton mouse is sometimes applied to it. Haacke himself believes, however, that the race originated either in China or Japan as the result of systematic selectional breeding. Of this he has no certainty, for he states that he failed to find any literature on the "beautiful mice of China and Japan." Whether Haacke's description of the dancing mouse was published elsewhere previous to its appearance in Brehm's "Tierleben" I am unable to state; I have found nothing written on the subject by him before 1890. Zoth (31 p. 176) also thinks that the race was developed by systematic breeding, or in other words, that it is a product of the skill of the Asiatic animal breeders.
Another account of the origin of the race is that accepted by Kishi (21 p. 481) and some other Japanese biologists. It is their belief that the forms of movement acquired by the individual as the result of confinement in narrow cages are inherited. Thus centuries of subjection to the conditions which Kishi has described (p. 6) finally resulted in a race of mice which breed true to the dance movement. It is only fair to add, although Kishi does not emphasize the fact, that in all probability those individuals in which the dancing tendency was most pronounced would naturally be selected by the breeders who kept these animals as pets, and thus it would come about that selectional breeding would supplement the inheritance of an acquired character. Few indeed will be willing to accept this explanation of the origin of the dancer so long as the inheritance of acquired characters remains, as at present, unproved.
Still another mode of origin of the mice is suggested by the following 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.
The occurrence of dancing individuals among common mice has been recorded by several other observers. Kammerer (20 p. 389)