SOME EXPERIMENTS OF LUTHER BURBANK. 207 



This is more likely to happen if the forces of natural or artificial selec- 

 tion were in its favor. There are many cases where the variant in 

 minor points is prepotent and outweighs the original stock. Mon- 

 strosities produced by crossing often perpetuate themselves as well as 

 the species does." 



" One difficulty with the mutation theory of Dr. De Vries, in my 

 opinion, is lack of sufficiently wide experimentation. Fuller investi- 

 gations will certainly show that the ' sports ' or ' chance ' variations 

 come under the same law as that of ' fluctuating ' variations, mutations 

 being only fluctuating variations carried beyond the critical point 

 where past fluctuating variations can not withstand the accumulated 

 forces without disintegration, thus bending them in a new direction." 



" Professor Hubrecht is certainly in error in stating that the mean 

 fluctuations can not be carried into the extreme or ' sport ' variations 

 by selection. Professor Hubrecht speaks of two divergent processes, 

 ' fluctuating variations ' and l mutations/ which he says : ' Darwin has 

 not sufficiently kept separate.' They are not separate; one is only a 

 tendency toward the other, and which continued, though latent, may, 

 or will, at last become dominant, so as to swing the fluctuating varia- 

 tions fully out of the old orbit into the ' mutation ' or ' sport 'condition. 

 Eadical changes of environment for a series of generations will produce 

 a tendency to sport, but hybridization will bring it about far more 

 abruptly, and for practical plant or animal breeding or for scientific 

 study of all these variations, far more satisfactorily." 



" The misunderstanding evidently comes from not having a clear 

 knowledge of latent and dominant hereditary forces. A knowledge of 

 these explains the whole matter and makes harmony between Darwin 

 and Wallace, leaving Professor De Vries's careful experiments good, but 

 coming to different conclusions on the results." 



" Professor Hubrecht also states that ' now for the first time — forty 

 years after the appearance of the ' Origin of Species ' — the actual birth 

 of a species has been observed by him.' As I have produced several 

 good species by hybridization, as good as nature herself has produced, 

 and as others have done the same by selection alone, the above sen- 

 tence is hardly true. But as before stated, hybridization followed by 

 selection is the shortest plan by which valid new species can be pro- 

 duced. In other words, the 'period of mutation' can he produced at 

 will!" 



" The mutation theory of the origin of species seems like a step 

 backward towards the special creation theory, and without any facts as 

 yet adequate to support it as a universal theory, however valuable and 

 suggestive the experiments of Dr. De Vries may be." 



" There is a remarkably close analogy between hybridization and 

 grafting. Bringing. over from France a primus (P. mirooolana var. 



