18 



FANCY MICE. 



colour. He urges that such cases as puppies in the same litter closely 

 resembling two distinct breeds are probably due to superfoetation, 

 that is, to the influence of two parents. Care, however, was taken of 

 the parentage of the mice in the cases I have given. 



*'It is very difficult to observe such facts as these without in a 

 measure accepting some theory akin to that of Mr. Darwin's ' pan- 

 generis.' If we conceive the black pigment in the rete mucosum of 

 the tail of uracoid mice as existing in a higher state of development 

 in the primordial ancestor of the genus Mus ; if we imagine it de- 

 veloped to a less degree in the typical grey Mus musculus ; and if 

 we suppose it almost entirely aborted in the albino mice then re- 

 appearing in the uracoid mouse, we have the theory of reversion or 

 atavism brought to its fair test of practical experience. It may then 

 appear that the theories of speculative biologists may be tested by 

 reference to an inexpensive and common animal, that breeds plenti- 

 fully, and may afford far more easy series of specimens than the 

 rarer and more valuable species. 



'* Bell is, as usual, excessively vague about the varieties of the com- 

 mon mouse. He gives as a character of the albino alone the fact 

 that it becomes exceedingly tame, running about the table, and 

 allowing itseK to be taken in the hand without manifesting any 

 alarm. But this psychological character connotes all other varieties 

 of tame mouse than that which has white hair and red eyes. He 

 speaks of a wild variety, of the ordinary size, nearly black above, 

 and very dark grey beneath, taken in Hertfordshire and Warwick- 

 shire. A vague description of this character, of course, precludes my 

 identification of such variety with my uracoid mice. Bell further 

 speaks of a pale grey variety, without the least mixture of brown ; 

 of an exceptional variety, at Wezford Hill, in which the mice were 

 of an unusually dark colour, especially along the dorsal line, which 

 was nearly black ; and he goes on to specify some of the other 

 varieties. He adopts the one from Pallas, of the ordinary colour, 

 more or less patched with white; and also speaks of a pale buff 

 variety, which is not rare. It is, of course, just possible that this 

 variety may be equivalent to the helvolus of Fischer. He states 

 that the grey, patched and pale buff varieties have the black eyes 

 of the common mouse, and are not, therefore, albinos. But the 

 arrangement of his sentences evidently leads us to imagine that 

 the pied mouse of India, the rick or barn mouse of Scotland, and 

 the grey Hertfordshire varieties are albinos. 



"I have probably said enough here respecting the breeds of mice. 

 Some experience, however, has not yet led me to observe the naked 

 mice which are described in the 'Proceedings Zoological Society* 

 (1856, p. 38), nor after many experiments in breeding and cross- 

 breeding all varieties and colours of mice does there appear to be any 

 tendency to the production of the breed which we may call really 

 piebald, i.e., of three colours, say black, white, and brown. The 

 term 'skewbald' was appUed by the late Dr. Gray to varieties of 

 horse that were tinted in two colours alone. We have the two- 

 coloured variety common in the wild mouse, as we have in the 



