396 THE EVIDENCE OF EVOLUTION. 



keep equal pace in the line of modification, no single one being 

 allowed to go distinctly ahead of the others. The whole family 

 gradually changes, and the consequence would be that the old form 

 disappears in the same degree as the new makes its appearance. 



This easy and plausible conception, however, is plainly contra- 

 dicted by the new facts. There is neither a gradual modification nor 

 a common change of all the individuals. On the contrary, the main 

 group remains wholly unali'ected by the production of new species. 

 After eighteen years it is absolutely the same as at the beginning, and 

 even the same as is found elscA^here in localities where no mutability 

 has been observed. It neither disappears nor dies out, nor is it ever 

 diminished or changed in the slightest degree. 



Moreover, according to the current conception, a changing species 

 would commonly be modified into only one other form, or at best 

 become split into two different types, separated from one another by 

 flowering at different seasons or by some other evident means of 

 isolation. My evening primrose, however, produces in the same 

 locality, and at the same time, from the same group of plants, quite 

 a number of new forms, diverging from their prototype in different 

 directions. 



Thence we must conclude that new species are produced sideways 

 by other forms, and that this change only affects the product, and 

 not the producer. The same original form can in this way give birth 

 to numerous others, and this single fact at once gives an exjjlanation 

 of all those cases in which species comprise numbers of subspecies, or 

 genera large series of nearly allied forms. Numerous other distinct 

 features of our prevailing classification may find on the same ground 

 an easy and quite natural explanation. 



To my mind, however, the real significance of the new facts is not 

 to be found in the substitution of a new conception for the now pre- 

 vailing ideas; it lies in the new w^ays which it opens for scientific 

 research. The origin of species is no longer to be considered as 

 something beyond our experience. It reaches within the limits of 

 direct observation and experiment. Its onl}'' real difficulty is the 

 rarity of its occurrence ; but this, of course, may be overcome by per- 

 severing research. Mutability is manifestly an exceptional state of 

 things if compared Avith the ordinary constancy. But it must occur 

 in nature here and there, and probably even in our immediate vicinity. 

 It has only to be sought for, and as soon as this is done on a suffi- 

 ciently large scale the study of the origin of species will become an 

 experimental science. 



New lines of work and new prospects will then be opened, and the 

 application of new discoveries and new laws on forage crops and 

 industrial plants Avill largely reward the patience and perseverance 

 required by the present initial scientific studies. 



