Xo. 544] 



ORIGIN OF UNIT CHARACTERS 



205 



Morgan's remarks (1912) on these positive experi- 

 ments are as follows : 



Castle has been very guarded in regard to the interpretation of the 

 results of selection in this ease. It is probable that ext. vine selection 

 is necessary to maintain the higher stage reached. It does not breed 



nothing permanent has been effected in the -crni-cclls ; and second, 

 that the result is due to the discovery of more extreme cases of fluctu- 



The general import of these experiments and opin- 

 ions is that fluctuations in the determiners, or genes, can 

 not be utilized to establish a new quantitative mean. It 

 is obvious that what have been measured by biometri- 

 cians as hereditary " fluctuations " might be regarded 

 as "saltations" of all degrees, but such saltations do 

 not represent new determiners in the Mendelian or 

 Johannsen sense; they are mere fluctuations in existing 

 determiners. Pure Mendelians would allege that tall- 

 ness in man or other mammals can only be accumulated 

 through the saltatory origin of "tall" determiners which 

 are not connected continuously through intermediate 

 forms with the antithetic "short" determiners. As to 

 stature Brownlee observes (1911, p. 255) :- ' 



6. Summary as to Discontinuitif mul Mmdelism 



phant branch of modern biology. Its contributions to 

 heredity are epoch-making. But heredity is the conserv- 



