IIJIO.] 



VARIETIES OF MUii UATTUS IN EGYPT. 



()G1 



(Jomparisou of^l. rattus and M. norvegicus. 



Passing now from M. rattiis to M. norveyicus .and comparing 

 Tables I. (text-fig. 58, p. 657) and IV. (text-fig. 61), we find a 

 striking and surprising analogy in the cui-ves. As in the rase 



Text-fig. 61. 



Length of Hindfoot in mm. 



. 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 



o 



Table IV. 

 Curve of liiiul-foot iiiciisiivenicuts of Mks iiorrefficns. 



of J/, raitus, M. norvegicas also shows three apices at 32, 37, and 

 39, but in this case there is no colour variation, and therefore no 



groups, for heing a separate mutation it might be found (if the hind-foot measure- 

 ment were taken as the determinant character of the subgroup) in two or more of 

 the subgroups. 



The answer to this objection according to our present knowledge is that in 

 any pai'ticular locality we have always found it associated with oi e, rtnd onlij one, 

 size of hind foot; that is to say, always in the .same subgroup a^ defined by 

 the size of the foot. Fui'thermore tiie breeding experiments, so lar as they have 

 gone, seem to point lo tlip faet that it is inherited in correlation with the >ize of the 

 hmd foot in the rats Irom Egypt. 



