UNIT-CHARACTERS (GENE MUTATIONS) 31 



expected of a unit-character, with a deficiency probably 

 due to its low viability. 



Waltzing (v) 



In 80 b.c. "in the ninth moon, a yellow mouse was found dancing with 

 its tail in its mouth in the gateway of the palace of the Kingdom of Yen 

 [now the province of Chili]. The animal danced incessantly. The king 

 asked the queen to feed it with wine and meat but this did not interfere 

 with the performance. The mouse died during the night. — Annals of the 

 Han Dynasty (translation by Quentin Pan). 



Waltzing mice (see Fig. 22) are unable to orient themselves 

 upon a horizontal plane, and this results in a rapid and erratic 

 turning or whirling. Waltzers make many turning, twist- 

 ing, and jerking head movements {183). Waltzers are totally 

 deaf {182). Different investigators disagree as to whether 

 or not the semicircular canals are morphologically normal. 

 Waltzers are very delicate, poor mothers, and quite suscep- 

 tible to cold. The most common inbred strain of Japanese 

 waltzers in America is non-agouti black and bears a high 

 grade of recessive piebald, with the anatomical characteristics 

 of Mus bactrianus (wagneri). Waltzing is inherited as a sim- 

 ple recessive (25, 31, 32, 61, 76). 



Gates (63) bred a waltzer containing but one dose of 

 waltzing, which presumably through a faulty cell division 

 had lost that portion of the normal chromosome which 

 contains the allelomorph of waltzing. Painter's histological 

 investigation (142) confirmed this conclusion. 



Shaker (sh) 



The mutation shows itself principally in the form of nervous head 

 movements. — Lord and Gates, 1928. 



The shaker (126) makes choreic head movements similar 

 to those of the waltzer but lacks the circling movements. 

 The character is recessive and linked with albinism and pink- 

 eyed dilution. 



Rodless retina (r) 



Microscopic sections of these eyes showed the total absence of visual 

 cells (rods). — Keeler, 1924. 



