GENERAL DISCUSSION. 93 



' In most black litters [of black Persian cats] at least one has a white 

 spot on chest or throat, and this generally settles the question which, if 

 any, shall join the majority at a tender age. The unfortunate kit's pedi- 

 igree may be absolutely devoid of offense on this point. Apparently no 

 precautions can prevent or eradicate the fault." 



From the instability of some characteristics we may infer that they 

 would be subponderant in heredity. Thus in Leighton, page 403, refer- 

 ring to the Dandie Dinmont terriers, we find the following: ' It is gener- 

 ally best to mate a mustard to a pepper to prevent the mustards becoming 

 too light in color, though two rich-colored mustards may be mated with 

 good results." 



On page 87, ' ' When brindle Great Danes are continuously bred together 

 it has been found that they get darker and that the peculiar striping dis- 

 appears and in that case the introduction of a good fawn into the strain is 

 advisable. The constant mating of harlequins (black spots on white) has 

 the tendency to make the black patches disappear and the union with a 

 good black Great Dane will prevent the loss of color." 



The tendency of most white breeds of poultry to become cream-colored 

 and of Barred Plymouth Rocks to become "smoky" asserts itself when- 

 ever selection of a good strain ceases. The stalwart Mendelian, in this 

 last case, has an explanation in the assumption that "smoky' Barred 

 is a unit-character, and that light Barred is only produced by the selection 

 of fluctuations and hence must inevitably fall back when selection ceases. 

 But this is nothing more or less than the assumption of the preponderance 

 of the type of the unit-character over its derivative. The stalwart Men. 

 delian then admits preponderance in fluctuations so long as they lead to a 

 unit-character. If, then, there is nothing intrinsically impossible about 

 preponderance, the only objection to it as a factor of evolution to the Men- 

 delian lies in his conception of clear-cut unit-characters having a perfect 

 segregation. Any belief in such sharply-cut phenomena is untenable in 

 the consideration of the color-pattern of these beetles, where some degree 

 of segregation is nevertheless positive. 



Cases of mass reversion are, to my mind, often the result of preponder- 

 ance of the reverting character over the newer conditions. Of course 

 reversion taking place in cases following the cessation of short, active 

 selection is to be attributed to regression. 



The degree of segregation in heredity is most perfect in spots 1-3 in 

 Hippodamia convergent. It varies by easy stages to cases in which the 

 heredity is nearly if not quite blending, as in the relation of 5 and 6 in 

 Epilachna borealis or as in the incomplete pronotal margin or in the size of 

 the pronotal dash in Hippodamia convergent. Just short of blended inher. 

 itance we have such cases as those in which the bulk of the individuals 

 lie between two extremes, at each of which many individuals are massed. 

 The result may be likened to the balls on a bowling alley, which, while 

 passing frequently the position of each pin, yet in the long run pass more 



