112 THE EVOLUTION OF LIVING BEINGS. 



„in central and Northern Europe." 



Walnut (Juglans regia). 

 Vol. I, p. 379. Description of different „ varieties" only. 



Nuts (Corylus avellana). 

 Vol. I, p. 379. Most botaniss rank all the varieties 

 under the same species, the common wild nut. 



Cucurbitaceous plants. 

 Vol. I, p. 384. ..Finally M. Naudin remarks that the 

 ..extraordinary production of races and varieties 

 by a single species and their permanence, when not 

 interfered with by crossing, are phenomena well 

 calculated to cause reflection. 



Trees. 

 Vol. I, p. 384. ..Deserve a passing notice on account 

 ..of the numerous varieties which they present." 



Flowers. 



Vol. I. p. 388. ..Many of our favourite kinds in their 

 present state are the descendants of two or more 

 species crossed and commingled together and this 

 circumstance alone would render it difficult to de- 

 tect the difference due to variation." 



As we see, a single originis/)yoweiiinno case, while an 

 origin from different sources by crossing, is made pro- 

 bable on the other hand in many cases. 



Darwin himself resumes the question in the follo- 

 wung sentence on p. 12 of the Origin: 



„In the case of most of our anciently domesticated 

 „animals and plants it is not possible to come to any 

 ..definite conclusion, whether they are descended from 

 ..one or several wild species" 



