No. 544] ORIGIN OF UNIT CHARACTERS 



will be all the Selection that we require for our evolutionary progress 

 [p. 89]. 



Thus Johannsen's general conception of the origin of 

 progressive or retrogressive new characters is that "it 

 is sufficient to state that the essential point in evolution 

 is the alteration, loss or gain of the genes or constit- 

 uents of the genotype ... all evidences as to 'muta- 

 tions' point to the discontinuity of the changes in ques- 

 tion.'' 



6. Negative Results of Experiments on Quantitative 

 Variation 



We agree with Johannsen that a delusive appearance 

 of continuity might arise through selection of degrees 

 of hereditary fluctuation in structure or function, for ex- 

 ample, of tallness or shortness of stature, of intensity or 

 faintness of color. Some Mendelians discard fluctua- 

 tions altogether as non-hereditary; thus Punnett (1911, 

 p. 138) 20 observes: "At the present time we have no 

 valid reason for supposing that they [fluctuations] are 

 ever inherited." 



The question, however, is not as to quantitative onto- 

 genic variations caused by favorable or unfavorable en- 

 vironment or by changes of habit, but as to heritable 

 fluctuations springing from the germ plasm. Experi- 

 ments have been directed to the point whether variations 

 in size, in proportion, etc., of unit characters as distin- 

 guished from the unit characters themselves are trans- 

 mitted. 



Davenport has reached negative results; he observes 

 (1910): 



In the last few decades the view has been widespread that char- 

 acters can be built up from perhaps nothing at all by select in;, >» • <>rk 

 generation the merely quantitative variation that goes farthest in the 

 desired direct!,,,,. The conclusion upon which De Vries laid the great- 

 est stress, that quantitative and qualitative characters differ funda- 

 mentally in their heritability, is supported by our experiment.- < p. . >>• 



