26 



more simply put but no less ingenious 

 and quite original idea of Galton's is 

 perhaps due to some extent to Galton 

 himself, for he has not seen fit in his 

 more recent publications to adhere to 

 his Stirp theory in the light of research 

 progress. The Stirp theory does not 

 correlate too well with Galton's Law 

 of Regression, it is true, but it could 

 scarcely be better supported or illus- 

 trated than by the results which I have 

 described: a usually complete regres- 

 sion to the genotype of a pure line 

 seems to me the most beautiful evi- 

 dence for a slightly modified Stirp 

 concept. It is true that Galton's Stirp 

 concept cannot be maintained un- 

 changed. Although Weismann •' very 

 recently regarded Galton as the 

 "voice" of cellular limitation through 

 "Determinants" — or however one 

 might name these theoretical hered- 

 itary corpuscles, de Vries deserves the 

 great credit for having recognized the 

 unitary nature of hereditary particles, 

 which he called "pangenes"— a concept 

 he first published in 1889 ^ and further 

 advanced in the "Mutationstheorie." It 

 seems to me that the Galton-de Vries 

 theory is the only truly useful theory 

 of heredity. 



JOHANNSEN 



Should the present publication be 

 successful in bringing the principle of 

 pure lines recognition as an absolutely 

 necessary principle in truly intensive 

 research in the study of heredity, then 

 its highest purpose would be achieved. 

 Later publications will attempt to illu- 

 minate the activity of lines which vary 

 polymodally. I have investigated only 

 unimodal variation in this paper,'^ in 

 order to present my concept in its 

 simplest instance. 



The train of thought which under- 

 lies this investigation is expressed in 

 its simplicity most clearly by the often 

 cited words of Goethe: 



"Dich im UnendHchen zu finden 

 Musst unterscheiden und dann 

 verbinden." ^ 



Vilmorin has emphasized the differ- 

 entiation of the parts, Galton has dem- 

 onstrated the legitimate basis for re- 

 combination; I have tried here to 

 combine the points of view for which 

 these two ingenious investigators are 

 honored. 



5 Weismann, Vortriige iiber die Descen- 

 denztheorie, 1902, p. 421. 



6 de Vries, "Intracellulare Pangenesis," 

 Jena, 1889. 



"^ de Vries has publislied a special case con- 

 cerning heredirv' in a pure "bimodal" line in 

 his Mutatio?2Stheorie (vol. 2, p. 509), based 

 on a short communication of mine. 

 8 "Before the infinite can be thine 

 You must first break it down and then 

 re-combine." 



