24 Mutability and Individual Variation. 



with it the assumption that the form under consideration 

 had been created as such. The reasonableness of this 

 position was recognized by both parties but especially 

 by GoDRON and Jordan. But at the present day when 

 the common origin of all species is hardly ever called in 

 question it is very difficult to judge this controversy fairly. 



The origin of a new form from another was termed 

 at that time a mutation.^ Godron and Jordan asserted 

 that every one of the forms constituting their species was 

 immutable. Jordan moreover tried to prove the truth 

 of this statement by breeding experiments. He recog- 

 nized individual variation and observed and recorded it 

 accurately.- He was also acquainted with local races^ 

 whose differences disappear whenever they are cultivated 

 for a few years next one another in the same soil ; he 

 knew moreover that as a rule it took only a few genera- 

 tions to effect this change. Further, he was familiar 

 with the results of accidental crosses by insects or wind, 

 and mentioned the genera {Cirsiiim etc.) in which this 

 was most apt to occur. 



But individual variability and mutability were abso- 

 lutely different things in his eyes ; he frequently observed 

 the first; but never saw an example^ of the latter. That 

 was why he held species to be immutable.^"* 



^ Already Lamarck used the terms "races muiahlcs on variables" ; 

 see GiARD, Discours d'ouverturc de J. B. Lamarck, 1907, page iii 

 (Note of 1908). 



^A. Jordan, De I'origine dcs arbrcs fniiticrs, 1853, p. 9. 



^ Loc. cit., p. 10 



* Besides the common Viola tricolor, V. arvensis (Murray) is 

 very familiar; it is reckoned by many authors as belonging to the 

 same species. Compare for example Koch, Synopsis Florae ger- 

 manicac et hclveticae. V. arvensis itself consists of a series of con- 

 stant forms of which our Fig. 4 shows some of the more important. 



^Jordan, De VOrigine des arbres fruifiers, 1853. Tn this work 

 and in the other essays Jordan always uses the words "niufation" 

 and "inimutabilite" where he is dealing with the supposed change of 



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