No. 566] SPOTTING IN MICE 77 



have given the following results. The generation num- 

 bers may be disregarded as they refer to another method 

 of classification. It is to be remembered that the parents 

 in the tabulation given below, are all "blaze" in 

 character. 



If the "blaze" is a true Mendelian recessive we should 

 expect all 434 offspring to have some white on them. 

 The figures show that 430 of the 434 are of this type; 

 that is to say, approximately 1 per cent, are self. 



It is possible to account for the occasional production 

 of selfs even if the "blaze" character is a true recessive, 

 if we supposed that there are supplementary factors 

 which may influence color development; and it is quite 

 conceivable that such is the case. 



The chief point of interest in the crosses given above 

 is that while spotting behaves in F, as a recessive, certain 

 of the F 2 spotted individuals fulfil the requirements of 

 dominant spotting by producing self offspring. 



The spotting came from a single individual and can 

 scarcely be considered to be of two distinct types. 



We may now consider the bearing of these results on 

 the work of Miss Durham and Hagedoorn. 



Miss Durham's Results 



Miss Durham (1908) gives a detailed account of a re- 

 cessive type of spotting in mice. The numbers she ob- 

 tained are extensive, and the case seems well established, 

 coming as it does in corroboration of the work of Cuenot, 

 Darbishire and others. In the same papers she records 

 the occurrence of a dominant spotted type of mice. Bate- 

 son (1909), commenting on the case, compares it with the 



