48 F. B. SUMNER AND R. R. IIUESTIS. 



that between the F t parents and their F., offspring (O.229). 1 This 

 condition is paralleled by that shown in Table II. for black, white 

 and color. It might be explained as due to the segregation of 

 factors in the F 2 generation, a process which would obviously 

 weaken the correlation between members of this generation and 

 their parents. In this connection it is also worth noting that the 

 coefficient of fraternal correlation is higher for the F 1 generation 

 (.356) than for the F., generation (.328), a fact which is in accord 

 with the same interpretation. 2 



IV. FOOT PIGMENTATION. 



The feet, prepared as above indicated, were graded according to 

 the depth of pigmentation in the skin of the soles. In the present 

 series, both feet of each specimen were independently graded, the 

 mean of the two recorded values (in the exceptional cases where 

 they differed) being employed. The following figures give the 

 means and standard deviations for the parent races and the two 

 generations of hybrids, the numbers being approximately the same 

 as in the case of the skins : 



Means. St. Dev. 



Ercniicits 0.45 + .03 0.48 + .022 



fratcrculus 2.02 4- .05 0.79 + .038 



F hybrids i .65 + .03 0.60 + .020 



F ( hybrids 1.72+ .04 0.7 1 + .028 



The three salient facts shown by the foregoing figures are (i) 

 the much heavier pigmentation of the feet of P. c. fratcrculus, as 

 compared with crcinicus, the mean difference being somewhat 

 greater than that between P. vianiculatus gauibcli and P. in. sonori- 

 ensis from the same two localities; (2) the intermediate position 

 of both hybrid genertions, which, however, average darker than the 

 mean of the two parental figures and (3) the greater variability of 

 the Fo generation as compared with the F : . We thus have much 

 the same situation here as in the case of the other characters which 

 have been discussed. 



1 It should be added, however, that this relation holds for only 3 of the 6 

 " characters," taken singly. 



2 The circumstance that the F o broods resulted, to a considerable extent from 

 the mating of sibs would tend to increase the second of these figures, and thus 

 to diminish the difference between the two hybrid generations in respect to fra- 

 ternal correlation. 



