No. 615] INHERITANCE IN FEROMYSCUS 



207 



tails and likewise larger feet than smaller animals. My 

 figures show that, even uheu animals of the same body 

 length are considered, those with longer tails tend, on the 

 whole, to have longer feet, and vice versa. To obtain 

 these results, I have computed the coefficients separately 

 for each size-group, containing ten or more individuals. 1 - 

 All but 5 of these 21 figures are positive, the mean being 

 + 0.27. Thus the greater tail and foot length of the Eu- 

 reka race may have arisen simultaneously, both being the 

 expression of a single constitutional change. 



One further word regarding the nature of these racial 

 differences, before we pass to a consideration of their 

 heredity. It is plain that, with a single possible excep- 

 tion, all of the differences thus far considered are lk sub- 

 stantive," rather than "meristic," to follow Bateson V 1 "' 

 terminology, or "proportional," rather than "numeri- 

 cal," to use terms recently employed by Osborn. 14 In no 

 case are they of the nature of "presenee-and-absence" 

 differences, such as figure so widely in Mendelian litera- 

 ture. Whether or not, on ultimate analysis, they can be 

 resolved into the latter category, will be discussed later. 



The differences without exception relate to means and 

 modes, as was illustrated above by histograms con- 

 structed for two of the characters (Figs. 5 and 8). The 

 frequency polygons commonly overlap broadly, when ad- 

 jacent members of the series are compared. We find an 

 approach to discontinuity only in a comparison of the 

 most widely divergent races. 



The single difference of a meristic or numerical char- 

 acter is that relating to the number of caudal vertebrae. 

 But even here the difference is one of averages, for no 

 single race seems to be characterized by the unvarying 

 presence of any particular number of vertebra?, as certain 

 larger taxonomic groups are characterized by a definite 

 number of teeth or mammae. It is worth mention also that 



12 Cf. Sumner, 1915, pp. 349-350, 409-415. 



