614 Validity of the Doctrine of Mutation. 



useless, although if applied to the pistil, it is capable of 

 producing an abundance of good seed. It is evident 

 that this condition cannot have arisen either by gradual 

 modifications or under the inliuence of the ordinary se- 

 lection of useful characters. 



All the difficulties which we have mentioned as be- 

 setting the current view, disappear if we substitute muta- 

 bility for fluctuating variability, as the source of the 

 origin of species ; and there is no doubt that adaptations 

 can be explained by mutability just as satisfactorily as 

 by fluctuating variability. 



§ 8. VEGETATIVE MUTATIONS. 



In order to conduct an experimental investigation 

 into the manner in which mutations arise, it is necessary 

 to know when they occur. According to the prevailing- 

 opinion this moment is assumed to be that of fertilization. 

 Gallesio clearly expressed this view at the beginning 

 of the last century, and advocated it against the belief 

 in the direct influence of the environment wliich was 

 common amongst breeders at that time.^ Some associa- 

 tion of species-forming ^•ariability with fertilization is 

 generally regarded as being clearly demonstrated both 

 in the animal and vegetable kingdoms, and especially for 

 annual plants and those which are ordinarily multi])lied 

 by seed. 



On the other hand we have the bud variations, or 

 vegetative mutations as they should rather be called. They 

 were well known to the older scientists, but Darwix was 

 the first to insist on their iniportance by collecting all 



' G. Gallesto, Tralfr du Citrus: Teoria delta rif^mduciouc vcge- 

 iahile, Pisa. i<St6; De Canpolle. Ptiysiologic vcgctalc. II. p. 720. 



