102 Miscellatiea 



The answer to the first questioii has been obtained, and it i.s in the negative : the aiiswer to 

 the second h;vs not, as the hybrids are not yet old enough to be paired. The expcrinients are as 

 yet only beginning ; but the cvidence concerning tlic cliai-acters of the first generation i.s already 

 greater than that obtained by von Ouaita, who only observed the result of crossing four pairs of 

 niico, while the litters already obfeiiued by me are the result of nine crosses. 



The Parent forms. 

 (a) The Japanese Waltzing Mice. 



The avcrage size of these mice is slightly smaller than that of the common housc mouse : 

 they are characterized by their facnlty of spinning round, which is due to abnormality of the 

 semicircular canals ; and by the restlessness of their demcanour when not dancing. The gromid 

 colour of their coat is pure white ; but there is always a variable amouut of pale fawn on the 

 cheeks, Shoulders and rump ; the arrangemeut of the colour on the mouse is seen in Fig. 1. 

 They have pink eyes. 



Our stock of waltzing mice arrived in December last : from that time tili August they bred 

 freely ; and in all cascs the offspring of two waltzing mice were indistinguishablc from their 

 parents, exccpt for slight difterences in the distribution of the fawn colour on the body : that is 

 to say the original stock are shown by the character of their oflFspring to have been pure-bred. 

 This fact is euiphasized in ordcr to removo any siispicion which niay arise in the mind of some 

 careful critic that the waltzing mice dealt with may have been dominant hybrids. 



(b) The Albino Mice. 



The mice used were the true albinos with pink eyes which are familiär to everj-one : they 

 may be roughly dividcd'into two categories : — 



(i) Piu-e4)red Albinos from the well-known moase breeder JIr Steer and others. 



(ii) Cro.ss-bred Albinos which have appearod from time to time in the litters of piebald 

 mice kept in the Oxford Laboratory for embryological purposes. 



The cross-bred albinos were used advisedly : for albinism is said to be a recessive character ; 

 and this being so any albino is perfectly piue regardless of ancestry: that is to say, on the 

 Mendelian hypothesis it makes no diflerence, as far as its offspring is concerned, whether a 

 certain albino is the chikl of pieWld parents or whether its imrents have been pure white 

 for many generations. 



On the Mendelian hypothesis the ancestry of the albinos should make no difference : we shall 

 soe that, as a matter of fact, it probably does. 



The Hybrids. 



The number of hybrid families in which the colours can be seen is at present nine. Tho 

 coloration of the hybrid ditVei-s from that of cither parent in the fact that with two exceptions 

 there are jwtches of colour which it is difficult to distinguish from that of the common housc 

 mouse. 



The hybrids can be roughly cliissified according to the distribution of this colour on their 

 bodies. 



(a) Mice in which the distribution of the gray colour corresponds roughly with the 

 distribution of fawn colour in the waltzing mouse. Fig. 2. 



(6) Mice in which the gray colom- Covers much more of the body. Fig. 3. 



