THE 



AMERICAN NATURALIST 



Vol. LI I. April-May, 1918 Nos. 616-617 



CONTINUOUS AND DISCONTINUOUS VARIA- 

 TIONS AND THEIR INHERITANCE IN 

 PEROMYSCUS 



DR. F. B. SUMNER 

 Scripps Institution, La Jolla, Calif. 



I. Introduction 



Many of the views which we are now accustomed to 

 associate with the names of Weismann, Bateson, DeVries, 

 Nilsson-Ehle and others were either foreshadowed or 

 clearly formulated by Francis Galton, many years earlier. 

 Galton's polygon, by which he illustrated the difference 

 between continuous and discontinuous variations, is 

 doubtless known to most readers; as is also his distinc- 

 tion between " blended" and ' ' particulate" inheritance. 

 It is less familiar, perhaps, that Galton regarded all in- 

 heritance as ' ' largely, i f n ot wholl y, ' particulate. ' ' ' Even 

 skin color, the classic example of blended inheritance in 

 man, is presumably "none the less 'particulate' in its 

 origin, but the result may be regarded as a fine mosaic 

 too minute for its elements to be distinguished in a gen- 

 eral view." Again, "the blending in stature is due to 

 its being the aggregate of the quasi-independent inheri- 

 tances of many separate parts" (1889, p. 139). 



Galton did not deny all heritability to those variations 

 which were represented by the minor oscillations of his 

 polygon, although he refers to such variations as "un- 

 stable." 



With the modern revival of Mendel's principles of 



