THROWING BACK 73 



mind until it comes to be considered separately. 

 The colour of the two varieties crossed will be first 

 briefly considered. 



The common albino mouse (Plate II., No. 1) has 

 a pure white coat ; there is no pigment in it at all. 

 The tail, hands, feet and ears are very pale pink, 

 and the eyes are a deep pink, the colour of these 

 organs being due to the blood in them. 



The Japanese waltzing mouse, with which I have 

 experimented, is coloured exactly Hke the albino 

 except that it possesses patches of fawn-yellow fur 

 on its shoulders and haunches. That is to say, it is 

 a fawn-and-white piebald with pink eyes (Plate II., 

 No. 2). The extent of these patches of fawn-yellow 

 fur varies very little from individual to individual 

 in this variety. 



A hybrid produced by mating these two varieties 

 is shown at No. 3. The coat is a dark grizzly grey, 

 hardly distinguishable from that of the house mouse ; 

 and the eyes are jet black. The tail may be either 

 deeply pigmented over its whole extent or, as in the 

 specimen shown, the dark pigment may not extend 

 over the whole of it. The hybrid shown at No. 3 

 is the usual result of mating mice Nos. 1 and 2. I 

 have, however, observed rare exceptions to it, but 

 these are usually attributable to the impurity of the 

 albino stock used, and need not detain us now. It 

 makes no difference to the result whether the albino 

 is the male and the fawn-and-white mouse the female 

 parent, or the albino is the female and the fawn-and- 

 white the male. 



