SUMMARY OF THE WORK 329 



In a word, a single case like that of the hybrid 

 blackberry-raspberry, described and depicted in 

 "New Creations" under the name of the Primus 

 berry, would seem by itself fairly to establish the 

 doctrine that new species of plants may arise by 

 the combination of old species. 



Stated otherwise, the case of the Primus berry 

 would seem to furnish unequivocal evidence as 

 to at least one way in which the problem of the 

 origin of new species might be answered. The 

 survival of the fittest had been explained as an 

 essential part of the Darwinian doctrine. The 

 origin of the fittest (or at least one possible 

 origin) appeared to be explained by the exist- 

 ence of such a hybrid as the Primus berry. 



The parents of the Primus berry, it will be 

 recalled, were the California dewberry (Rubus 

 ur sinus] and the Siberian raspberry (Rubus 

 cratcegifolius] . Not only are these forms so 

 different in appearance that no botanist would 

 ever think of denying that they belong to totally 

 different species, but the fact that one of them is 

 indigenous to California and the other to Siberia 

 gives what might be called geographical support 

 to the opinions of the classifiers. Few indeed are 

 the forms of animal or plant life inhabiting the 

 Eastern and the Western Hemispheres that are 

 recognized as specifically identical. 



